initscripts: Add switch to start processes in background

initscripts: Add switch to start processes in background

Since systemd, many programs no longer behave like a well-behaved
daemon. To avoid any extra solutions, this patch adds a -b switch which
will start a program in the background and throw away any output.

The behaviour remains unchanged for any other programs.

Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>
Signed-off-by: Arne Fitzenreiter <arne_f@ipfire.org>