Fix JDWP ObjectRegistry lock ordering.

Also make debugging lock ordering violations nicer by using our
LockLevel operator<<.

Change-Id: Ic15ebe70363a90a09f6491bd5c336a604e9d6c48
diff --git a/src/thread.cc b/src/thread.cc
index 0d3c5b9..ca97e89 100644
--- a/src/thread.cc
+++ b/src/thread.cc
@@ -644,7 +644,7 @@
       }
       // Release locks and come out of runnable state.
     }
-    for (int i = kMaxMutexLevel; i >= 0; --i) {
+    for (int i = kLockLevelCount - 1; i >= 0; --i) {
       BaseMutex* held_mutex = Thread::Current()->GetHeldMutex(static_cast<LockLevel>(i));
       if (held_mutex != NULL) {
         LOG(FATAL) << "Holding " << held_mutex->GetName()