Remove Tunnel Token and allow re-registration to the tunelling service. (#2123)
Remove Tunnel Token and allow re-registration to the tunelling service. (#2123)

* Added helper scripts to change the tunnel registration settings without
having to reflash the SD card. The `redo-tunnel-registration.sh` is for
the time when user skipped the `tunnel-registration`. And
`remove-tunnel-token.sh` if user wants to change re-registration to a
new tunnel subdomain.

* Merged the scripts for tunnel re-registration

mozilla-iot/gateway,moziot/gateway,mozilla-iot/gateway,mozilla-iot/gateway,mozilla-iot/gateway,moziot/gateway,moziot/gateway,mozilla-iot/gateway