Use correct logging level when null metadata is detected during showT…

…able(). (#3477)

The logging level is current ERROR which is inaccurate.  It can be WARN.

corfudb-tools/src/main/java/org/corfudb/browser/CorfuStoreBrowserEditor.java

@@ -254,7 +254,7 @@ private int printTableRegistry() {
     private void printMetadata(Map.Entry<CorfuDynamicKey, CorfuDynamicRecord> entry) {
         StringBuilder builder;
         if (entry.getValue().getMetadata() == null) {
-            log.error("metadata is NULL");
+            log.warn("metadata is NULL");
             return;
         }
         try {