VOL-3588 Update OFAgent to support new version of protos

Change-Id: Ic3944779f9a600ebcd5d7a916616f473059e311e
diff --git a/vendor/github.com/gogo/protobuf/proto/encode.go b/vendor/github.com/gogo/protobuf/proto/encode.go
index 3abfed2..9581ccd 100644
--- a/vendor/github.com/gogo/protobuf/proto/encode.go
+++ b/vendor/github.com/gogo/protobuf/proto/encode.go
@@ -189,6 +189,8 @@
 // prefixed by a varint-encoded length.
 func (p *Buffer) EncodeMessage(pb Message) error {
 	siz := Size(pb)
+	sizVar := SizeVarint(uint64(siz))
+	p.grow(siz + sizVar)
 	p.EncodeVarint(uint64(siz))
 	return p.Marshal(pb)
 }