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/db/model/root.go b/db/model/root.go
index 0f14c7c..8f9e001 100644
--- a/db/model/root.go
+++ b/db/model/root.go
@@ -104,6 +104,7 @@
 	} else {
 		r.node.MergeBranch(txid, false)
 		r.ExecuteCallbacks()
+		r.DeleteTxBranch(txid)
 	}
 }