[V3] Make region_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 region_client use **kwargs.

Partially implements blueprint consistent-service-method-names

Change-Id: Icde61f9b50bbf3269ede0074d70396355e83b755
2 files changed