Sonar related fixes

- suppress SONAR warning for printing stack trace in CLI
- add string constants for the Sonar suppression identifiers

Change-Id: I03992f89675f9d074347042b7a196dbcc1036c28
diff --git a/utils/misc/src/main/java/org/onlab/packet/IGMP.java b/utils/misc/src/main/java/org/onlab/packet/IGMP.java
index cabd252..938cd6e 100644
--- a/utils/misc/src/main/java/org/onlab/packet/IGMP.java
+++ b/utils/misc/src/main/java/org/onlab/packet/IGMP.java
@@ -15,21 +15,21 @@
  */
 package org.onlab.packet;
 
-import org.slf4j.Logger;
-
 import java.nio.ByteBuffer;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
-import java.util.Arrays;
+
+import org.slf4j.Logger;
 
 import static com.google.common.base.MoreObjects.toStringHelper;
 import static com.google.common.base.Preconditions.checkNotNull;
 import static org.onlab.packet.PacketUtils.checkInput;
+import static org.onlab.util.SonarSuppressionConstants.SONAR_SWITCH_FALLTHROUGH;
 import static org.slf4j.LoggerFactory.getLogger;
 
-
 /**
  * Implements IGMP control packet format.
  */
@@ -156,7 +156,7 @@
      *
      * @return the serialized IGMP message
      */
-    @java.lang.SuppressWarnings("squid:S128") // suppress switch fall through warning
+    @java.lang.SuppressWarnings(SONAR_SWITCH_FALLTHROUGH) // suppress switch fall through warning
     @Override
     public byte[] serialize() {
         byte [] data = new byte[8915];