HDFS-11054. Suppress verbose log message in BlockPlacementPolicyDefault. Contributed by Chen Liang.

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/BlockPlacementPolicyDefault.java

@@ -1030,9 +1030,11 @@ public class BlockPlacementPolicyDefault extends BlockPlacementPolicy {
       }
       firstOne = false;
       if (cur == null) {
-        LOG.warn("No excess replica can be found. excessTypes: {}." +
-            " moreThanOne: {}. exactlyOne: {}.", excessTypes, moreThanOne,
-            exactlyOne);
+        if (LOG.isDebugEnabled()) {
+          LOG.debug("No excess replica can be found. excessTypes: {}." +
+              " moreThanOne: {}. exactlyOne: {}.", excessTypes,
+              moreThanOne, exactlyOne);
+        }
         break;
       }