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

Premature commit due to misreading CR feedback.

This reverts commit r215301.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@215302 91177308-0d34-0410-b5e6-96231b3b80d8