YARN-5096 addendum. Turned another logging statement to debug. Contributed by Sangjin Lee.

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-timelineservice/src/main/java/org/apache/hadoop/yarn/server/timelineservice/storage/common/ColumnHelper.java

@@ -258,7 +258,9 @@ public class ColumnHelper<T> {
 
           String columnName = null;
           if (columnPrefixBytes == null) {
-            LOG.info("null prefix was specified; returning all columns");
+            if (LOG.isDebugEnabled()) {
+              LOG.debug("null prefix was specified; returning all columns");
+            }
             // Decode the spaces we encoded in the column name.
             columnName = Separator.decode(columnKey, Separator.SPACE);
           } else {