[V3] Make endpoints_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 endpoints_client use **kwargs.

Partially implements blueprint consistent-service-method-names

Change-Id: Id00c386fbf075e2fa66cdf0604c5068e65f4e344
3 files changed