ServerConnection: dispose internal objects
ServerConnection: dispose internal objects

Bug: https://bugs.freedesktop.org/show_bug.cgi?id=64923
Reviewed-by: Simon McVittie <2b470b34502dbf3ba4bcc04ea7e64f4e0e104f33@collabora.co.uk>

freedesktop-unofficial-mirror/telepathy__telepathy-idle,freedesktop-unofficial-mirror/telepathy__telepathy-idle,freedesktop-unofficial-mirror/telepathy__telepathy-idle