Fix service validation schema

In case when nova has 'servicegroup_driver' not 'db'
field 'updated_at' in services response is null.

Change-Id: I03610827b87719b76c043b85f1f9002869eb4a5e
Closes-Bug: 1387983
Don't setup identity v3 client if v3 is disabled

Some tests report failures about the identity v3 url not being
specified, even if api_v3 is set to false in tempest.conf.

Change-Id: Ifb5c6c8bd154373d33c90236ff37fcc5b8759405
Closes-Bug: #1389742
Fixes volume client in volume tests

volumes_client is coming from cls.os and volume_client is coming
from cls.os_adm. Here it creates a naming disaster for the volume
client. Adding admin_volume_client at the place of volume_client
fixes the client for admin user.

Change-Id: I0c55d3f7fbf4a096c012ffee3697f14869fe9962
Fix tox stress invocation to not quote arguments

Change-Id: I6fc1e64c3e52a02126235d5cc42831ee2d25f997
Merge "Fix service validation schema"
Merge "Don't setup identity v3 client if v3 is disabled"
Merge "Fixes volume client in volume tests"
Merge "Fix tox stress invocation to not quote arguments"