Add mock to test-requirements
Add mock to test-requirements

Mock is used for get_module_from_path tests. This will ensure
it gets installed for testing purposes.

Change-Id: I31baa61a531b3018f19664a437fe05c0c8461e4d

chair6/bandit,pombredanne/bandit,austin987/bandit,pombredanne/bandit,stackforge/bandit,stackforge/bandit