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

Change-Id: I1aa2774beb6b7ed7419bc45aeb53fcae8a8ecda0
diff --git a/vendor/github.com/grpc-ecosystem/grpc-gateway/runtime/proto_errors.go b/vendor/github.com/grpc-ecosystem/grpc-gateway/runtime/proto_errors.go
index ca76324..3fd30da 100644
--- a/vendor/github.com/grpc-ecosystem/grpc-gateway/runtime/proto_errors.go
+++ b/vendor/github.com/grpc-ecosystem/grpc-gateway/runtime/proto_errors.go
@@ -44,12 +44,12 @@
 	w.Header().Del("Trailer")
 
 	contentType := marshaler.ContentType()
-	// Check marshaler on run time in order to keep backwards compatability
+	// Check marshaler on run time in order to keep backwards compatibility
 	// An interface param needs to be added to the ContentType() function on
 	// the Marshal interface to be able to remove this check
-	if httpBodyMarshaler, ok := marshaler.(*HTTPBodyMarshaler); ok {
+	if typeMarshaler, ok := marshaler.(contentTypeMarshaler); ok {
 		pb := s.Proto()
-		contentType = httpBodyMarshaler.ContentTypeFromMessage(pb)
+		contentType = typeMarshaler.ContentTypeFromMessage(pb)
 	}
 	w.Header().Set("Content-Type", contentType)