Add support for IPv4 fallback when IPv6 cannot be established

[claudijd]

Basically, if we have an endpoint that supports both IPv6 and IPv4 on the same hostname (ssh.example.com) and that endpoint has records for both IPv6 and IPv4, but only IPv4 has a listening SSH service we will likely not handle that scenario. This issue is to make sure ssh_scan does have the smarts to handle that gracefully.

[jinankjain]

@claudijd One way to handle this we could do first try with IPv6 version if that fails then in the catch block of that we could do for IPv4. Am I correct?

[claudijd]

@jinankjain yeah, that could work

[jinankjain]

@claudijd then I would implement that after fixing #112 #104