Adds v2 keystone service test to service v3

This submission adds missing v3 tests in test_services.py
when compared with v2 test_services.py. Also added corresponding
support functions to service_client.py.

Change-Id: I73d44af9851cbfb33b490a313b1c2808c291840a
Merge "Adds v2 keystone service test to service v3"