daemon: Make an extra process for keepalive.

Versions of pycurl that are linked against NSS have
some trouble with this multi-process architecture.
So we don't connect to anywhere in the master process
that each worker process creates its own SSL context.
Remove the urlgrabber fork hack.
daemon: Make shutting down a bit faster.

First, send SIGTERM to all processes and then wait
until they all have finished.
system: Fix free memory.
Check if there is a progressbar, when calling finish.