Allow passing user_id to v2Password plugin
Allow passing user_id to v2Password plugin

Whilst this is undocumented it is supported by keystone and relied upon
by other services.

Change-Id: Idf8be75e2e0b275d9c9840082079100dd13a70ff

citrix-openstack-build/keystoneauth,sileht/keystoneauth,jamielennox/keystoneauth