VOL-1497 : Add more control to kv/memory access

- Added kv locking mechanism (etcd only)
- (watch) control path access whenever possible
- (watch) use a transaction for updates and merge with memory
- cleaned up vendoring
- misc changes to fix exceptions found along the way

Amendments:

- Copyright header got removed in auto-generated file
- Changed default locking to false for KV list operation
- Updated backend api to allow the passing of locking parameter

Change-Id: Ie1a55d3ca8b9d92ae71a85ce42bb22fcf1419e2c
diff --git a/vendor/go.etcd.io/etcd/clientv3/txn.go b/vendor/go.etcd.io/etcd/clientv3/txn.go
index c3c2d24..c19715d 100644
--- a/vendor/go.etcd.io/etcd/clientv3/txn.go
+++ b/vendor/go.etcd.io/etcd/clientv3/txn.go
@@ -18,7 +18,7 @@
 	"context"
 	"sync"
 
-	pb "github.com/coreos/etcd/etcdserver/etcdserverpb"
+	pb "go.etcd.io/etcd/etcdserver/etcdserverpb"
 
 	"google.golang.org/grpc"
 )