[V3] Make groups_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 groups_client use **kwargs.

Partially implements blueprint consistent-service-method-names

Change-Id: I558453a64247835b117f4612064a381ad84f3513
3 files changed