Fix issues found by FindBugs: RCN_REDUNDANT_NULLCHECK_OF_NULL_VALUE

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

Note: The warning in FlowPusher.createQueue() is suppressed for now,
because it is not clear what the right solution is.

Change-Id: Id5716121692093400c9854910dfd7a61e20474e9
diff --git a/src/main/java/net/onrc/onos/core/flowprogrammer/FlowPusher.java b/src/main/java/net/onrc/onos/core/flowprogrammer/FlowPusher.java
index 0bcb001..fe29efd 100644
--- a/src/main/java/net/onrc/onos/core/flowprogrammer/FlowPusher.java
+++ b/src/main/java/net/onrc/onos/core/flowprogrammer/FlowPusher.java
@@ -18,6 +18,8 @@
 import java.util.concurrent.locks.Lock;
 import java.util.concurrent.locks.ReentrantLock;
 
+import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
+
 import net.floodlightcontroller.core.FloodlightContext;
 import net.floodlightcontroller.core.IFloodlightProviderService;
 import net.floodlightcontroller.core.IOFMessageListener;
@@ -572,6 +574,8 @@
     }
 
     @Override
+    @SuppressFBWarnings(value = "RCN_REDUNDANT_NULLCHECK_OF_NONNULL_VALUE",
+                        justification = "Future versions of createQueueImpl() might return null")
     public boolean createQueue(IOFSwitch sw) {
         SwitchQueue queue = createQueueImpl(sw);