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/vendor/github.com/opencord/voltha-lib-go/v2/pkg/db/kvstore/client.go b/vendor/github.com/opencord/voltha-lib-go/v2/pkg/db/kvstore/client.go
index c0ebe5f..97fbec9 100644
--- a/vendor/github.com/opencord/voltha-lib-go/v2/pkg/db/kvstore/client.go
+++ b/vendor/github.com/opencord/voltha-lib-go/v2/pkg/db/kvstore/client.go
@@ -79,10 +79,10 @@
 
 // Client represents the set of APIs a KV Client must implement
 type Client interface {
-	List(key string, timeout int, lock ...bool) (map[string]*KVPair, error)
-	Get(key string, timeout int, lock ...bool) (*KVPair, error)
-	Put(key string, value interface{}, timeout int, lock ...bool) error
-	Delete(key string, timeout int, lock ...bool) error
+	List(key string, timeout int) (map[string]*KVPair, error)
+	Get(key string, timeout int) (*KVPair, error)
+	Put(key string, value interface{}, timeout int) error
+	Delete(key string, timeout int) error
 	Reserve(key string, value interface{}, ttl int64) (interface{}, error)
 	ReleaseReservation(key string) error
 	ReleaseAllReservations() error