Unstub the passed object when calling unstub()

Previously, only the global was unstubbed when StubObject::unstub() was
called. Now, the object given as a parameter will also be unstubbed.
(What about other references to the object, though?)

Change-Id: I431ddd61e24686fc2f014c30064808ce57fe1706
(cherry picked from commit 0d847cb55d8e9c3c0f40827828472fd9b25e1018)
Merge "Unstub the passed object when calling unstub()" into wmf/1.24wmf12