Make image_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 image_client use **kwargs.
This patch doesn't cover create/update_image because these methods
are used at many places and it is nice to separate them from this
patch for easy implementation/review.

Partially implements blueprint consistent-service-method-names

Change-Id: I1976623d512cf3f622d81805d68cc994d359cf74
3 files changed