8047290: Make Mutex::_no_safepoint_check_flag locks verify that this lock never checks for safepoint

Ensure consistent safepoint checking in Mutex/Monitor locking methods.

Reviewed-by: dholmes, dcubed, coleenp

hotspot/src/share/vm/gc_implementation/shared/concurrentGCThread.cpp

@@ -88,7 +88,8 @@ static void _sltLoop(JavaThread* thread, TRAPS) {
 
 SurrogateLockerThread::SurrogateLockerThread() :
   JavaThread(&_sltLoop),
-  _monitor(Mutex::nonleaf, "SLTMonitor"),
+  _monitor(Mutex::nonleaf, "SLTMonitor", false,
+           Monitor::_safepoint_check_sometimes),
   _buffer(empty)
 {}