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

Change-Id: I1aa2774beb6b7ed7419bc45aeb53fcae8a8ecda0
diff --git a/vendor/github.com/golang/snappy/decode.go b/vendor/github.com/golang/snappy/decode.go
index 72efb03..f1e04b1 100644
--- a/vendor/github.com/golang/snappy/decode.go
+++ b/vendor/github.com/golang/snappy/decode.go
@@ -52,6 +52,8 @@
 // Otherwise, a newly allocated slice will be returned.
 //
 // The dst and src must not overlap. It is valid to pass a nil dst.
+//
+// Decode handles the Snappy block format, not the Snappy stream format.
 func Decode(dst, src []byte) ([]byte, error) {
 	dLen, s, err := decodedLen(src)
 	if err != nil {
@@ -83,6 +85,8 @@
 }
 
 // Reader is an io.Reader that can read Snappy-compressed bytes.
+//
+// Reader handles the Snappy stream format, not the Snappy block format.
 type Reader struct {
 	r       io.Reader
 	err     error