Make attach_volume 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 attach_volume use **kwargs.

Partially implements blueprint consistent-service-method-names

Change-Id: Ibc7f5c80755876318e1f5c7f7548276f315467c6
10 files changed