Ceph

The problem here is that tcp_read never times out, and OSDs don't write to sessions unless they're replying to something. So once formed, a connection hangs around until the client says to kill it (which can't happe if they die or lose their network)!
I've begun fixing this by setting a timeout on the tcp socket, but initial testing is revealing odd problems.

Since the OSD isn't losing thread references and I've got another bug that's an actual error, I'm going to move to that and come back to this.