[VOL-2193] Create mocks for Kafka Client and Etcd

This commit consists of:
1) A kafka client mock that implements the kafka client interface
under voltha-lib-go/pkg/kafka/client.go
2) An embedded Etcd server that runs in-process and represents an
Etcd server.

Change-Id: I52a36132568e08c596bb4136918bebcb654a3b99
diff --git a/VERSION b/VERSION
index 98c938e..f2b42fc 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-2.2.12
+2.2.13