Make set_flavor_extra_spec 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 set_flavor_extra_spec use **kwargs.

Partially implements blueprint consistent-service-method-names

Change-Id: I7907a03744f2eb95fed65acb008f962665a4977b
3 files changed