VOL-2154 : Moving back db/model to voltha-go repo

- Package imports and dockerfiles updated
- Left backend.go in voltha-lib-go

Amendments:

- Adjusted proto imports in unit tests
- Adjusted references to db/model in unit tests
- Integrate voltha-lib-go updates

Change-Id: I2d168c516a238222f0371a7bcb672d2b06796838
diff --git a/go.mod b/go.mod
index 13a4c52..7b506c3 100644
--- a/go.mod
+++ b/go.mod
@@ -8,7 +8,7 @@
 	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 v2.2.9
+	github.com/opencord/voltha-lib-go/v2 v2.2.10
 	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