VOL-1903: Cleanup Makefile to use consistent versions of protoc/grpc-gateway

Change-Id: I10a9918cab7e5b34901f3529fb629f4fa0f0f185
(cherry picked from commit d52eaeea409ac4d88b9b9366c811e3f38ff42667)
diff --git a/go.mod b/go.mod
index 256b8fe..f969c82 100644
--- a/go.mod
+++ b/go.mod
@@ -15,4 +15,5 @@
 	golang.org/x/sync v0.0.0-20190423024810-112230192c58
 	google.golang.org/genproto v0.0.0-20190716160619-c506a9f90610
 	google.golang.org/grpc v1.22.1
+	gopkg.in/jcmturner/goidentity.v3 v3.0.0 // indirect
 )