[analyzer] MisusedMovedObject: Fix state-resetting a base-class sub-object.

If a method is resetting the state of an object that was moved from, it should
be safe to use this object again. However if the method was defined in a parent
class, but used in a child class, the reset didn't happen from the checker's
perspective.

Differential Revision: https://reviews.llvm.org/D31538

llvm-svn: 315301