Make identity v3 roles_client use **kwargs

As we discussed on
http://lists.openstack.org/pipermail/openstack-dev/2015-July/068864.html
All http POST/PUT methods need to contain **kwargs as their arguments.
This patch makes identity v3 roles_client use **kwargs.

Also rename some method to match the consistency across v2 and v3
service client

Partially implements blueprint consistent-service-method-names

Change-Id: I2737c3a9c448c16440d2707b31fa3f99876d25a0
8 files changed