Fix go generate for protobuf

Signed-off-by: Santhosh Manohar <santhosh@docker.com>

libnetwork/networkdb/networkdb.go

@@ -1,6 +1,6 @@
 package networkdb
 
-//go:generate protoc -I.:../Godeps/_workspace/src/github.com/gogo/protobuf  --gogo_out=import_path=github.com/docker/libnetwork/networkdb,Mgogoproto/gogo.proto=github.com/gogo/protobuf/gogoproto:. networkdb.proto
+//go:generate protoc -I.:../vendor/github.com/gogo/protobuf --gogo_out=import_path=github.com/docker/libnetwork/networkdb,Mgogoproto/gogo.proto=github.com/gogo/protobuf/gogoproto:. networkdb.proto
 
 import (
 	"fmt"