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

- Kept backend.go to limit impact in other components

Amendments:

- Removed db/model unit tests
- Forgot to fix some stash merges
- Removed unused "lock" parameter from kv clients
- Changed version for release

Change-Id: I25a03eb335ce22d49412be4bf2cceaff387dc4ae
diff --git a/pkg/db/kvstore/client.go b/pkg/db/kvstore/client.go
index c0ebe5f..97fbec9 100644
--- a/pkg/db/kvstore/client.go
+++ b/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