connection: only disconnect if we're not already disconnected
connection: only disconnect if we're not already disconnected

If we don't check this, tp-glib will give us a nice big fat warning.

Signed-off-by: Jonny Lamb <3d1fb3642aaab2ff70e3392a5ab916bf99eed6a3@collabora.co.uk>

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