Make routers_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 routers_client use **kwargs.

Partially implements blueprint consistent-service-method-names

Change-Id: I2db862191cc30bcf903098d2959b9b22b16c153b
8 files changed