floating ip pollster should trap error from lack of ip addresses

If the central pollster for floating ips finds none, it does not trap the error raised by the database layer.

2012-09-25 06:29:09 WARNING ceilometer.central.manager [-] Continuing after error from network_floatingip: Zero floating ips exist.

2012-09-25 06:29:09 ERROR ceilometer.central.manager [-] Zero floating ips exist.

2012-09-25 06:29:09 TRACE ceilometer.central.manager Traceback (most recent call last):

2012-09-25 06:29:09 TRACE ceilometer.central.manager File "/opt/stack/ceilometer/ceilometer/central/manager.py", line 66, in periodic_tasks

2012-09-25 06:29:09 TRACE ceilometer.central.manager for c in pollster.get_counters(self, context):

2012-09-25 06:29:09 TRACE ceilometer.central.manager File "/opt/stack/ceilometer/ceilometer/network/floatingip.py", line 33, in get_counters

2012-09-25 06:29:09 TRACE ceilometer.central.manager ips = manager.db.floating_ip_get_all(context)

2012-09-25 06:29:09 TRACE ceilometer.central.manager File "/opt/stack/nova/nova/db/api.py", line 323, in floating_ip_get_all

2012-09-25 06:29:09 TRACE ceilometer.central.manager return IMPL.floating_ip_get_all(context)

2012-09-25 06:29:09 TRACE ceilometer.central.manager File "/opt/stack/nova/nova/db/sqlalchemy/api.py", line 111, in wrapper

2012-09-25 06:29:09 TRACE ceilometer.central.manager return f(*args, **kwargs)

2012-09-25 06:29:09 TRACE ceilometer.central.manager File "/opt/stack/nova/nova/db/sqlalchemy/api.py", line 882, in floating_ip_get_all

2012-09-25 06:29:09 TRACE ceilometer.central.manager raise exception.NoFloatingIpsDefined()

2012-09-25 06:29:09 TRACE ceilometer.central.manager NoFloatingIpsDefined: Zero floating ips exist.