Make add_router_to_l3_agent 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 add_router_to_l3_agent of network client
to use **kwargs.

Partially implements blueprint consistent-service-method-names

Change-Id: I2f17062076a3a356bbb2f67099bcc9b3edd2f76f
3 files changed