[VOL-2235] Mocks and interfaces for rw-core

This update consists of mocks that are used by the rw-core
during unit testing.  It also includes interfaces used for unit
tests.

Change-Id: I20ca1455c358113c3aa897acc6355e0ddbc614b7
diff --git a/go.mod b/go.mod
index a4c8b07..91f0efe 100644
--- a/go.mod
+++ b/go.mod
@@ -8,9 +8,10 @@
 	github.com/golang/protobuf v1.3.2
 	github.com/google/uuid v1.1.1
 	github.com/gyuho/goraph v0.0.0-20160328020532-d460590d53a9
-	github.com/opencord/voltha-lib-go/v2 v2.2.12
+	github.com/opencord/voltha-lib-go/v2 v2.2.13
 	github.com/opencord/voltha-protos/v2 v2.0.1
 	github.com/phayes/freeport v0.0.0-20180830031419-95f893ade6f2
 	github.com/stretchr/testify v1.4.0
+	google.golang.org/appengine v1.4.0 // indirect
 	google.golang.org/grpc v1.24.0
 )