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/github.com/gogo/protobuf/proto/extensions.go b/vendor/github.com/gogo/protobuf/proto/extensions.go
index 44ebd45..686bd2a 100644
--- a/vendor/github.com/gogo/protobuf/proto/extensions.go
+++ b/vendor/github.com/gogo/protobuf/proto/extensions.go
@@ -544,7 +544,7 @@
 	}
 	typ := reflect.TypeOf(extension.ExtensionType)
 	if typ != reflect.TypeOf(value) {
-		return errors.New("proto: bad extension value type")
+		return fmt.Errorf("proto: bad extension value type. got: %T, want: %T", value, extension.ExtensionType)
 	}
 	// nil extension values need to be caught early, because the
 	// encoder can't distinguish an ErrNil due to a nil extension