Remove mox3 in test-requirement.txt of senlinclient
Remove mox3 in test-requirement.txt of senlinclient

mox3 was used for unit tests. But now we replace it with mock.
So I think there no need to keep it in test-requirement.txt.

Change-Id: I9170a3943e4e5b3c2c5a947ec04dc49726a7e423

stackforge/python-senlinclient,openstack/python-senlinclient,stackforge/python-senlinclient,openstack/python-senlinclient