McdConnection: if dropped (connected -> disconnected) more than 3 times in 2 minutes, stop reconnecting
McdConnection: if dropped (connected -> disconnected) more than 3 times in 2 minutes, stop reconnecting

Also apply exponential backoff to reconnects within the first 2 minutes.

Previously, if connecting to a server that allowed us to connect but then
immediately dropped us again, we'd go into a tight loop, without the
benefit of the usual backoff algorithm.

freedesktop-unofficial-mirror/telepathy__telepathy-mission-control,freedesktop-unofficial-mirror/telepathy__telepathy-mission-control,freedesktop-unofficial-mirror/telepathy__telepathy-mission-control,freedesktop-unofficial-mirror/telepathy__telepathy-mission-control