mutexLocker assert_locked_or_safepoint should not access VMThread state from non-VM-thread

See here:

void assert_locked_or_safepoint(const Mutex* lock) {
  // check if this thread owns the lock (common case)
  assert(lock != NULL, "Need non-NULL lock");
  if (lock->owned_by_self()) return;
  if (SafepointSynchronize::is_at_safepoint()) return;
  if (!Universe::is_fully_initialized()) return;
  // see if invoker of VM operation owns it
  VM_Operation* op = VMThread::vm_operation();
  if (op != NULL && op->calling_thread() == lock->owner()) return;
  fatal("must own lock %s", lock->name());
}

The call to VMThread::vm_operation() does not check if the calling thread is VMThread. This would fail the assert after JDK-8212107.