Add some extra checks to the MoveOnly test class to ensure it is not...

Add some extra checks to the MoveOnly test class to ensure it is not constructed or assigned from in a moved-from state.

Some tests were constructing it with 0, so use -1 as the invalid state
instead.

Reviewers: Marshall Clow

Differential Revision: http://reviews.llvm.org/D4095

llvm-svn: 215301