Make volumes_extensions_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 volumes_extensions_client use **kwargs.

Partially implements blueprint consistent-service-method-names

Change-Id: Ie7f61741d54a629a15b1e2b8fce178ebc06176d3
6 files changed