Check if port forwards are established otherwise restart tunnel

[JayGoldberg]

Ran into an instance where the tunnels were open, but the reverse ports were not assigned on the remote host. Likely because they were already assigned at the instantiation of the tunnel (again). Normally in interactive you'd see "could not set up port forwarding" or similar. We should either check for that, or possibly increase the sleep before a tunnel is brought back up to allow the remote end to close the port.

When tunnel is already running, make sure we are verifying that data can be sent through forwarded ports.