address review comments

Author: Apache9

hbase-server/src/main/java/org/apache/hadoop/hbase/master/assignment/RegionStateNodeLock.java

@@ -71,7 +71,9 @@ private void lock0(Object lockBy) {
   }
 
   private boolean tryLock0(Object lockBy) {
-    lock.lock();
+    if (!lock.tryLock()) {
+      return false;
+    }
     try {
       if (owner == null) {
         owner = lockBy;