connectivity: enhance shutdown handling and first packets

This patch embeds multiple litte fixes detected while working on swarms:
+ When stopping an account, shutdownConnections() should be done
before dht->join() to avoid any lock (because some io::run() are done).
+ Also, some channel were not awoken when clearing sockets.
+ channelDatas_ must be locked while accessed
+ setOnRecv() can be done after first packets on channel, so to avoid
to miss first packets, re-inject current stored datas.

Change-Id: I1d1335b5b6873b281c5357d18121a4bb525646f8