[VOL-4290] Voltha go library updates for gRPC migration

Change-Id: I1aa2774beb6b7ed7419bc45aeb53fcae8a8ecda0
diff --git a/vendor/github.com/grpc-ecosystem/grpc-gateway/runtime/marshaler.go b/vendor/github.com/grpc-ecosystem/grpc-gateway/runtime/marshaler.go
index 98fe6e8..4615329 100644
--- a/vendor/github.com/grpc-ecosystem/grpc-gateway/runtime/marshaler.go
+++ b/vendor/github.com/grpc-ecosystem/grpc-gateway/runtime/marshaler.go
@@ -19,6 +19,13 @@
 	ContentType() string
 }
 
+// Marshalers that implement contentTypeMarshaler will have their ContentTypeFromMessage method called
+// to set the Content-Type header on the response
+type contentTypeMarshaler interface {
+	// ContentTypeFromMessage returns the Content-Type this marshaler produces from the provided message
+	ContentTypeFromMessage(v interface{}) string
+}
+
 // Decoder decodes a byte sequence
 type Decoder interface {
 	Decode(v interface{}) error
@@ -43,6 +50,6 @@
 
 // Delimited defines the streaming delimiter.
 type Delimited interface {
-	// Delimiter returns the record seperator for the stream.
+	// Delimiter returns the record separator for the stream.
 	Delimiter() []byte
 }