Rework the daemonization sequence

The current fork+close fds sequence has deficiencies which are hard to
work around:
  - logging can start logging before we fork (e.g. if we need to emit
    messages related to master checking), and thus use FDs which we
    can't track nicely
  - the queue locks the queue file, and again this fd needs to be kept
    open which is hard from the main loop (and this error is currently
    hidden by the fact that we don't log it)

Given the above, it's much simpler, in case we will fork later, to close
file descriptors right at the beginning of the program, and in Daemonize
only close/reopen the stdin/out/err fds.

In addition, we also close() the handlers we remove in SetupLogging so
that the cleanup is more thorough.

Reviewed-by: imsnah