Fix a test that was never being run, mark it XFAIL

Turns out this has always been crashing since the test landed in
r186647:

  Assertion failed: (Access != AS_none && "Access specifier is AS_none inside a record decl"), function CheckAccessDeclContext, file clang/lib/AST/DeclBase.cpp, line 690.

Needs attention.

llvm-svn: 194072