Update service test case - V3

Adds a test_services.py test script so as to validate the update
service. And the rescpective support methods to "service_client.py"
in both json and xml interfaces

Change-Id: Ic088861049a2642076bbca166c84f234dfb6a290
Implements: blueprint keystone-v3-service-api-test
Merge "Update service test case - V3"
Adding new test for iSCSI live block migration

Requrires a new config value as the test depends on a
specific patch being made to XAPI to support the
relax-xsm-sr-check behaviour

Change-Id: I81cc39fed392fce9dfbda5683ffba29eeba936be
Fixup

Change-Id: Id2daaf1b10bf5534841d3b85a8a606fc4a7922f2