When spying on bound methods that were really defined on a parent of an

owning class, we cloned the method so that the underlying bytecode

wouldn't be shared between the spied method and other subclasses of the

parent. The same needs to be done for unbound methods as well.
This updates our cloning logic to properly clone unbound methods,

keeping the state separate. This works on all supported versions of

Python.

Unit tests pass on all supported Python versions.
Tested against broken behavior in tests being written in Review Board.