[problem] On SSH connection errors failure reason indicates failure to connect to public IP

[nemesifier]

When SSH connections are attempted, the management IP is tried first, the last_ip is tried as last. If both failed, the error reason is the failure to the last IP.

It's normal to think that the system is trying to connecto the last_ip, but that is not the case. The error message is misleading.

Maybe a better approach could be to show both failures.

Tryinig the last_ip is needed for situations in which OpenWISP can reach the devices on last_ip too.

However, another approach could be to decide that OpenWISP shall try reaching devices only using the management_ip. The monitoring module has a setting for this. In this case we should rework a few things here too.