Fix Sonar critical flagged bugs

Change-Id: I60e9f72a1a66f65366d7dbc5335922e75097c9f3
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 594b79d..cabd252 100644
--- a/utils/misc/src/main/java/org/onlab/packet/IGMP.java
+++ b/utils/misc/src/main/java/org/onlab/packet/IGMP.java
@@ -156,6 +156,7 @@
      *
      * @return the serialized IGMP message
      */
+    @java.lang.SuppressWarnings("squid:S128") // suppress switch fall through warning
     @Override
     public byte[] serialize() {
         byte [] data = new byte[8915];