Add force detach volume test.

This patch adds the force detach volume test to
test_volume_actions_rbac, which enforces the following policy
action:

    volume_extension:volume_admin_actions:force_detach

for the force_detach endpoint [0].

[0] https://github.com/openstack/cinder/blob/master/cinder/api/contrib/admin_actions.py#L130

Change-Id: I4442f97012572bb2bfb398ba5593d742b920f13e
1 file changed