avserver: remove daemon mode

avserver: remove daemon mode

This code spews a multitude of warnings with glibc (unchecked
return values), some of them possibly warranted.  Furthermore,
the deamonisation is not suitable for use with typical startup
scripts as it does not provide the PID of the daemon in any way.
Users wishing to run avserver as a daemon can still do so using
start-stop-daemon or equivalent tools.

Signed-off-by: Mans Rullgard <mans@mansr.com>
Signed-off-by: Janne Grunau <janne-libav@jannau.net>