Keystone's auth_type is confusingly used as auth_strategy

The vnc_api.py is confusing auth_type with auth_strategy. This causes extensions (lbaasv2 haproxy loadbalancer in my case) not to load if the auth_type is properly defined in the neutron.conf.

If the auth_type is not defined, the vnc_api and extensions are defaulting to keystone and neutron plugin starts working correctly. I've checked these branches:

R3.1
R3.1.1.x
R3.2

The master contains a workaround, reading the auth_strategy as auth_type, but this disables possibility to use different keystone auth_type like token, certs, saml2 in the future.

I suggest introduce new parameter auth(n)_strategy in configuration files and VncApi constructor, defaulting to keystone.