Separated daemonize from dropping permissions.

Signed-off-by: Nikos Mavrogiannopoulos <nmav@gnutls.org>
If system provides a daemon(0,0) use it.

That makes sniproxy follow system conventions (e.g., in linux
daemon() does not need to fork twice, something that systemd
relies on).

Signed-off-by: Nikos Mavrogiannopoulos <nmav@gnutls.org>
remove any old pidfile

Signed-off-by: Nikos Mavrogiannopoulos <nmav@gnutls.org>
Merge pull request #60 from nmav/simplify-startup

Simplify startup