Move response code checking to client for v3 identity tests

test_Create_update_delete_policy had  a call to get_policy where the
result was not used at all so I removed it.

Partially Implements blueprint: client-checks-success

Change-Id: I06718380aa337886908c06f8fb7312c5f0c89f6a
Merge "Move response code checking to client for v3 identity tests"