net: fix dns lookup for android

`V4MAPPED` isn't supported by Android either (as of 6.0)

PR-URL: https://github.com/nodejs/node/pull/4580


Reviewed-By: Brian White <mscdex@mscdex.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>