package/minidlna/S60minidlnad: add force-reload to rebuild DB

Add a force-reload operation that restarts minidlnad and makes it
rebuild its database. This is what Debian does, and this is useful when
media_dir is changed in the configuration file or when inotify can not
detect changes inside the media directories (e.g. in case of a mount).

Signed-off-by: Benoît Thébaudeau <benoit@wsystem.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>