SIPMediaChannel: map a 404 status code to GroupChangeReason.Offline
SIPMediaChannel: map a 404 status code to GroupChangeReason.Offline

The reason is, many proxies return this status code for known user
names which are currently offline.

20070920152058-5b6ca-69e919c676d15eb2a3c0d349fd3297192f38c008.gz

freedesktop-unofficial-mirror/telepathy__telepathy-rakia,freedesktop-unofficial-mirror/telepathy__telepathy-rakia,freedesktop-unofficial-mirror/telepathy__telepathy-rakia