Init: retry stop when graceful stop takes long

Current init script waits only one second for gunicorn to stop. This
is probably shorter than the graceful timeout configured in gunicorn.

 - Rework the stop code so it is increasingly insistent:
   - Have start-stop-daemon send a -QUIT, then wait max 10 seconds.
   - Then send a -TERM, so everyone just quits.
   - Then send a -KILL, this is after 20 seconds of no response.

Also, remove the || true parts and replace them with --oknodo.
Merge pull request #32 from ByteInternet/retry-on-stop

Init: retry stop when graceful stop takes long