VOL-2664 Avoid overwriting vlan-filter-tasks in queue

-tag_add check is done in vlan-filter-task for add and remove cases.
-also a few log corrections are done.

Change-Id: Iec969bbbb9bffdf1236601b6a182eb0a88012416
diff --git a/python/requirements.txt b/python/requirements.txt
index 85c6640..4733885 100644
--- a/python/requirements.txt
+++ b/python/requirements.txt
@@ -1,2 +1,2 @@
 voltha-protos==3.2.3
-pyvoltha==2.3.15
+pyvoltha==2.3.18