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

Change-Id: I1aa2774beb6b7ed7419bc45aeb53fcae8a8ecda0
diff --git a/vendor/google.golang.org/grpc/stream.go b/vendor/google.golang.org/grpc/stream.go
index 134a624..bb99940 100644
--- a/vendor/google.golang.org/grpc/stream.go
+++ b/vendor/google.golang.org/grpc/stream.go
@@ -488,7 +488,7 @@
 	pushback := 0
 	hasPushback := false
 	if cs.attempt.s != nil {
-		if to, toErr := cs.attempt.s.TrailersOnly(); toErr != nil || !to {
+		if !cs.attempt.s.TrailersOnly() {
 			return err
 		}