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

Change-Id: I1aa2774beb6b7ed7419bc45aeb53fcae8a8ecda0
diff --git a/vendor/github.com/cespare/xxhash/v2/go.mod b/vendor/github.com/cespare/xxhash/v2/go.mod
new file mode 100644
index 0000000..49f6760
--- /dev/null
+++ b/vendor/github.com/cespare/xxhash/v2/go.mod
@@ -0,0 +1,3 @@
+module github.com/cespare/xxhash/v2
+
+go 1.11