YARN-4710. Reduce logging application reserved debug info in FSAppAttempt#assignContainer (Contributed by Yiqun Lin via Daniel Templeton)

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/fair/FSAppAttempt.java

@@ -771,8 +771,8 @@ public class FSAppAttempt extends SchedulerApplicationAttempt
   }
 
   private Resource assignContainer(FSSchedulerNode node, boolean reserved) {
-    if (LOG.isDebugEnabled()) {
-      LOG.debug("Node offered to app: " + getName() + " reserved: " + reserved);
+    if (LOG.isTraceEnabled()) {
+      LOG.trace("Node offered to app: " + getName() + " reserved: " + reserved);
     }
 
     Collection<SchedulerRequestKey> keysToTry = (reserved) ?