SSH tunnel is not re-connecting

If the SSH tunnel breaks for any reason, for example due to a reboot of the remote server, or due to a temporary network outage, Beaver will not try to re-connect the tunnel and will be stuck in a loop, continuously failing to connect through the broken tunnel.

Please see the attached pull request. It's my attempt at implementing a simple auto-reconnect mechanism. I've tested it with CentOS 6.