Fix issues found by FindBugs: BC_UNCONFIRMED_CAST

http://findbugs.sourceforge.net/bugDescriptions.html#BC_UNCONFIRMED_CAST

Change-Id: Ibd1019db95d85b316854be230473c716016d4275
diff --git a/src/main/java/net/onrc/onos/core/devicemanager/OnosDeviceManager.java b/src/main/java/net/onrc/onos/core/devicemanager/OnosDeviceManager.java
index ae4202a..99c8769 100644
--- a/src/main/java/net/onrc/onos/core/devicemanager/OnosDeviceManager.java
+++ b/src/main/java/net/onrc/onos/core/devicemanager/OnosDeviceManager.java
@@ -107,7 +107,8 @@
 
     @Override
     public Command receive(IOFSwitch sw, OFMessage msg, FloodlightContext cntx) {
-        if (msg.getType().equals(OFType.PACKET_IN)) {
+        if (msg.getType().equals(OFType.PACKET_IN) &&
+            (msg instanceof OFPacketIn)) {
             OFPacketIn pi = (OFPacketIn) msg;
 
             Ethernet eth = IFloodlightProviderService.bcStore.