Adds a mock.patch.stopall to the base unit test case cleanup routines to stop patches by default in unit tests. This behavior can be overwritten by setting an attribute on the test class if required. Also removes the explicit stops in the Cisco n1kv, VMware, and NEC unit tests to leverage the new automatic cleanup. Closes-Bug: #1290550 Change-Id: Ic642430a765ea8deb07ebd88b619da58a58e0edd