VOL-2485: Clear gemport from local cache when gemport is deleted

Once the gemport is released for a given onu, it also has to
be cleared from local cache which was used for deriving the
gemport->logicalPortNo during packet-in.
Otherwise stale info continues to exist after gemport is freed
and wrong logicalPortNo is conveyed to ONOS during packet-in
OF message.

Change-Id: I02059f0966583ecb2e2b22e65006c9194fb0570f
diff --git a/VERSION b/VERSION
index 276cbf9..32d1656 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-2.3.0
+2.3.1-dev