Fixed a memory leak in FlowPusher seen when switch is removed (ONOS-1573).

Change-Id: I2ccfc2b6ead31e72adf4b84a017571e77dde72c0
diff --git a/src/main/java/net/onrc/onos/core/flowprogrammer/FlowProgrammer.java b/src/main/java/net/onrc/onos/core/flowprogrammer/FlowProgrammer.java
index b5912d5..838533d 100644
--- a/src/main/java/net/onrc/onos/core/flowprogrammer/FlowProgrammer.java
+++ b/src/main/java/net/onrc/onos/core/flowprogrammer/FlowProgrammer.java
@@ -127,6 +127,7 @@
         if (ENABLE_FLOW_SYNC) {
             synchronizer.interrupt(sw);
         }
+        pusher.deleteQueue(sw, true);
     }
 
     @Override