[Gingerbread] Workaround for SaneAsyncTask: copy AsyncTask from KitKat

AsyncTask before Honeycomb didn't have the executeOnExecutor method
and always used its own thread pool. Luckily the new code works on
Gingerbread as-is, looks like. I hope.

Change-Id: I42231c7152b97a7676b7192e3c1b0ac8433b99d4