Make SecurityGroupAPI use Object instead of instance_get_by_uuid()

This patch makes the SecurityGroupAPI use the SecurityGroup object
for querying the list of security group names instead of pulling
the instance by id, and then following the ['groups'] link.

This is part of a set aimed at deprecating the instance_get_by_uuid()
method on conductor.

Related to blueprint compute-manager-objects-juno

Change-Id: Id69c2019e934cef72c9b06caa503ea74f28720ce
Don't translate debug level logs in nova.virt

Our translation policy
(https://wiki.openstack.org/wiki/LoggingStandards#Log_Translation) calls
for not translating debug level logs. This is to help prioritize log
translation. Furthermore translation has a performance overhead, even if
the log isn't used (since nova doesn't support lazy translation yet).

Change-Id: I524b48f530d8afd59a067074332e3964426e4d70
Merge "Don't translate debug level logs in nova.virt"
Merge "Make SecurityGroupAPI use Object instead of instance_get_by_uuid()"