Support activating library policy
Support activating library policy

This commit adds support in client library for create_policy to 
accept params 'library_policy' as expected by server for activating 
a library policy. Change needed by dashboard, for activating library
policy.

Change-Id: I0c4a70002bd172c0b5842cc7de1c9bb5ad0bcf5a
Closes-Bug:#1731194

openstack/python-congressclient