UOA provider plugins should each return a different GType

- Install account-plugin-empathy from the PPA
- Try adding an ICQ account and hit cancel
- Try adding a Groupwise account

The control center crashes trying to re-register the plugin.

(gnome-control-center:6227): GLib-GObject-WARNING **: cannot register existing type `EmpathyAccountsPlugin'

#0 g_logv (log_domain=0x7ffff616f94e "GLib-GObject", log_level=G_LOG_LEVEL_WARNING,
    format=0x7ffff6177568 "cannot register existing type `%s'",
    args1=args1@entry=0x7fffffffcd48) at /build/buildd/glib2.0-2.33.8/./glib/gmessages.c:765
#1 0x00007ffff5e8f032 in g_log (log_domain=log_domain@entry=0x7ffff616f94e "GLib-GObject",
    log_level=log_level@entry=G_LOG_LEVEL_WARNING, format=<optimized out>)
    at /build/buildd/glib2.0-2.33.8/./glib/gmessages.c:792
#2 0x00007ffff61660c5 in check_type_name_I (
    type_name=type_name@entry=0x7fffc24cc8af "EmpathyAccountsPlugin")
    at /build/buildd/glib2.0-2.33.8/./gobject/gtype.c:743
#3 0x00007ffff616618b in g_type_register_static (parent_type=93825000817792,
    type_name=0x7fffc24cc8af "EmpathyAccountsPlugin", info=info@entry=0x7fffffffce80,
    flags=flags@entry=0) at /build/buildd/glib2.0-2.33.8/./gobject/gtype.c:2725
#4 0x00007ffff616639d in g_type_register_static_simple (parent_type=<optimized out>,
    type_name=<optimized out>, class_size=<optimized out>, class_init=<optimized out>,
    instance_size=<optimized out>, instance_init=<optimized out>, flags=0)
    at /build/buildd/glib2.0-2.33.8/./gobject/gtype.c:2693
#5 0x00007fffc22c5c34 in empathy_accounts_plugin_get_type () at empathy-accounts-plugin.c:29
#6 0x00007fffcd6d270c in ap_client_load_plugin (account=0x555555dea290)
    at libaccount-plugin/client.c:90
#7 0x00007fffcdb0221d in cc_credentials_authorization_page_set_account (self=0x555555ca27e0,
    value=value@entry=0x555555dea290) at src/cc-credentials-authorization-page.c:403
#8 0x00007fffcdb034c2 in cc_credentials_preferences_on_accounts_page_new_account_request (
    provider_name=<optimized out>, self=0x555555929740) at src/cc-credentials-preferences.c:298
#9 _cc_credentials_preferences_on_accounts_page_new_account_request_cc_credentials_accounts_page_new_account_request (_sender=<optimized out>, provider_name=<optimized out>,
    self=0x555555929740) at src/cc-credentials-preferences.c:447
#10 0x00007ffff6148f37 in g_cclosure_marshal_VOID__STRINGv (closure=0x555555cc1800,
    return_value=<optimized out>, instance=0x555555bb1360, args=<optimized out>,
    marshal_data=<optimized out>, n_params=<optimized out>, param_types=0x5555559305d0)
    at /build/buildd/glib2.0-2.33.8/./gobject/gmarshal.c:1004
#11 0x00007ffff6146307 in _g_closure_invoke_va (closure=0x555555cc1800, return_value=0x0,
    instance=0x555555bb1360, args=0x7fffffffd318, n_params=1, param_types=0x5555559305d0)
    at /build/buildd/glib2.0-2.33.8/./gobject/gclosure.c:840
#12 0x00007ffff615faa8 in g_signal_emit_valist (instance=instance@entry=0x555555bb1360,
    signal_id=signal_id@entry=302, detail=detail@entry=0,
    var_args=var_args@entry=0x7fffffffd318)
    at /build/buildd/glib2.0-2.33.8/./gobject/gsignal.c:3211
#13 0x00007ffff61606f0 in g_signal_emit_by_name (instance=0x555555bb1360,
    detailed_signal=0x7fffcdb09e85 "new-account-request")
    at /build/buildd/glib2.0-2.33.8/./gobject/gsignal.c:3393
#14 0x00007ffff6148f37 in g_cclosure_marshal_VOID__STRINGv (closure=0x555555cbb8c0,
    return_value=<optimized out>, instance=0x555555bb15a0, args=<optimized out>,
    marshal_data=<optimized out>, n_params=<optimized out>, param_types=0x555555c23c70)
    at /build/buildd/glib2.0-2.33.8/./gobject/gmarshal.c:1004
#15 0x00007ffff6146307 in _g_closure_invoke_va (closure=0x555555cbb8c0, return_value=0x0,
    instance=0x555555bb15a0, args=0x7fffffffd7c8, n_params=1, param_types=0x555555c23c70)
    at /build/buildd/glib2.0-2.33.8/./gobject/gclosure.c:840
#16 0x00007ffff615faa8 in g_signal_emit_valist (instance=instance@entry=0x555555bb15a0,
    signal_id=signal_id@entry=310, detail=detail@entry=0,
    var_args=var_args@entry=0x7fffffffd7c8)
    at /build/buildd/glib2.0-2.33.8/./gobject/gsignal.c:3211
#17 0x00007ffff61606f0 in g_signal_emit_by_name (instance=instance@entry=0x555555bb15a0,
    detailed_signal=detailed_signal@entry=0x7fffcdb09e85 "new-account-request")
    at /build/buildd/glib2.0-2.33.8/./gobject/gsignal.c:3393
#18 0x00007fffcdb0571c in cc_credentials_providers_page_add_account_for_current_selection (
    self=self@entry=0x555555bb15a0, providers_tree=providers_tree@entry=0x555555c00390)
    at src/cc-credentials-providers-page.c:674
#19 0x00007fffcdb05880 in cc_credentials_providers_page_on_providers_tree_button_press_event (
    event=<optimized out>, widget=<optimized out>, self=0x555555bb15a0)
    at src/cc-credentials-providers-page.c:738
#20 _cc_credentials_providers_page_on_providers_tree_button_press_event_gtk_widget_button_press_event (_sender=_sender@entry=0x555555c00390, event=<optimized out>,
    self=self@entry=0x555555bb15a0) at src/cc-credentials-providers-page.c:413
#21 0x00007ffff7691d2c in _gtk_marshal_BOOLEAN__BOXED (closure=0x555555ca0280,
    return_value=0x7fffffffdb10, n_param_values=<optimized out>, param_values=0x7fffffffdbc0,
    invocation_hint=<optimized out>, marshal_data=<optimized out>)
    at /build/buildd/gtk+3.0-3.5.10/./gtk/gtkmarshalers.c:85
#22 0x00007ffff6146040 in g_closure_invoke (closure=0x555555ca0280,
    return_value=0x7fffffffdb10, n_param_values=2, param_values=0x7fffffffdbc0,
    invocation_hint=0x7fffffffdb60) at /build/buildd/glib2.0-2.33.8/./gobject/gclosure.c:777
#23 0x00007ffff6157d10 in signal_emit_unlocked_R (node=node@entry=0x555555783160,
    detail=detail@entry=0, instance=instance@entry=0x555555c00390,
    emission_return=emission_return@entry=0x7fffffffdc90,
    instance_and_params=instance_and_params@entry=0x7fffffffdbc0)
    at /build/buildd/glib2.0-2.33.8/./gobject/gsignal.c:3551
#24 0x00007ffff615f70a in g_signal_emit_valist (instance=0x555555c00390,
    signal_id=<optimized out>, detail=0, var_args=var_args@entry=0x7fffffffde18)
    at /build/buildd/glib2.0-2.33.8/./gobject/gsignal.c:3310
#25 0x00007ffff61601e2 in g_signal_emit (instance=instance@entry=0x555555c00390,
    signal_id=<optimized out>, detail=detail@entry=0)
    at /build/buildd/glib2.0-2.33.8/./gobject/gsignal.c:3356
#26 0x00007ffff77d650e in gtk_widget_event_internal (widget=widget@entry=0x555555c00390,
    event=event@entry=0x555555ce06d0) at /build/buildd/gtk+3.0-3.5.10/./gtk/gtkwidget.c:6298
#27 0x00007ffff77d6929 in gtk_widget_event (widget=widget@entry=0x555555c00390,
    event=event@entry=0x555555ce06d0) at /build/buildd/gtk+3.0-3.5.10/./gtk/gtkwidget.c:5955
#28 0x00007ffff768fc75 in propagate_event_up (topmost=<optimized out>, event=<optimized out>,
    widget=0x555555c00390) at /build/buildd/gtk+3.0-3.5.10/./gtk/gtkmain.c:2400
#29 propagate_event (widget=<optimized out>, event=0x555555ce06d0, captured=<optimized out>,
    topmost=0x0) at /build/buildd/gtk+3.0-3.5.10/./gtk/gtkmain.c:2500
#30 0x00007ffff76919eb in gtk_main_do_event (event=0x555555ce06d0)
    at /build/buildd/gtk+3.0-3.5.10/./gtk/gtkmain.c:1713