Add unit tests for "server lock" command.
Add unit tests for "server lock" command.

Change-Id: I0396fc4836ee918298bbe3860b7c1f42d3b97e33
Implements: blueprint osc-unit-test-framework-improvement

dtroyer/python-openstackclient,BjoernT/python-openstackclient,redhat-openstack/python-openstackclient,redhat-openstack/python-openstackclient,dtroyer/python-openstackclient,openstack/python-openstackclient,openstack/python-openstackclient,BjoernT/python-openstackclient