<rdar://problem/13267210> Ensure that Sema::CompareReferenceRelationship returns consistent results with invalid types.

When Sema::RequireCompleteType() is given a class template
specialization type that then fails to instantiate, it returns
'true'. On subsequent invocations, it can return false. Make sure that
this difference doesn't change the result of
Sema::CompareReferenceRelationship, which is expected to remain stable
while we're checking an initialization sequence.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@178088 91177308-0d34-0410-b5e6-96231b3b80d8