Fix recursive Policy patching

When using test.unit.patch_policies on a TestCase that subclasses a patched
TestCase the mock policies would be unwound too early.  This change allows you
to subclass a TestCase decorated with patch_policies and get the parent
classes effective POLICIES.

Change-Id: I1b5baefe1ae4281e3be8a5f772994aff4065f981
Merge "Fix recursive Policy patching" into feature/ec