Add rescue for ENOPROTOOPT errors

[J12934]

Hello 👋
I was scanning a network with ssh_scan but was always crashing at the same host with the following error code:

/usr/local/lib/ruby/2.6.0/socket.rb:1213:in `__connect_nonblock': Protocol not available - connect(2) for 192.168.42.42:22 (Errno::ENOPROTOOPT)
        from /usr/local/lib/ruby/2.6.0/socket.rb:1213:in `connect_nonblock'
        from /usr/local/lib/ruby/2.6.0/socket.rb:56:in `connect_internal'
        from /usr/local/lib/ruby/2.6.0/socket.rb:137:in `connect'
        from /usr/local/lib/ruby/2.6.0/socket.rb:641:in `block in tcp'
        from /usr/local/lib/ruby/2.6.0/socket.rb:227:in `each'
        from /usr/local/lib/ruby/2.6.0/socket.rb:227:in `foreach'
        from /usr/local/lib/ruby/2.6.0/socket.rb:631:in `tcp'
        from /usr/local/bundle/gems/ssh_scan-0.0.41/lib/ssh_scan/client.rb:48:in `block in connect'
        from /usr/local/lib/ruby/2.6.0/timeout.rb:93:in `block in timeout'
        from /usr/local/lib/ruby/2.6.0/timeout.rb:33:in `block in catch'
        from /usr/local/lib/ruby/2.6.0/timeout.rb:33:in `catch'
        from /usr/local/lib/ruby/2.6.0/timeout.rb:33:in `catch'
        from /usr/local/lib/ruby/2.6.0/timeout.rb:108:in `timeout'
        from /usr/local/bundle/gems/ssh_scan-0.0.41/lib/ssh_scan/client.rb:47:in `connect'
        from /usr/local/bundle/gems/ssh_scan-0.0.41/lib/ssh_scan/scan_engine.rb:75:in `scan_target'
        from /usr/local/bundle/gems/ssh_scan-0.0.41/lib/ssh_scan/scan_engine.rb:184:in `block (2 levels) in scan'
/usr/local/lib/ruby/2.6.0/socket.rb:1213:in `__connect_nonblock': Protocol not available - connect(2) for 192.168.42.42:22 (Errno::ENOPROTOOPT)
        from /usr/local/lib/ruby/2.6.0/socket.rb:1213:in `connect_nonblock'
        from /usr/local/lib/ruby/2.6.0/socket.rb:56:in `connect_internal'
        from /usr/local/lib/ruby/2.6.0/socket.rb:137:in `connect'
        from /usr/local/lib/ruby/2.6.0/socket.rb:641:in `block in tcp'
        from /usr/local/lib/ruby/2.6.0/socket.rb:227:in `each'
        from /usr/local/lib/ruby/2.6.0/socket.rb:227:in `foreach'
        from /usr/local/lib/ruby/2.6.0/socket.rb:631:in `tcp'
        from /usr/local/bundle/gems/ssh_scan-0.0.41/lib/ssh_scan/client.rb:48:in `block in connect'
        from /usr/local/lib/ruby/2.6.0/timeout.rb:93:in `block in timeout'
        from /usr/local/lib/ruby/2.6.0/timeout.rb:33:in `block in catch'
        from /usr/local/lib/ruby/2.6.0/timeout.rb:33:in `catch'
        from /usr/local/lib/ruby/2.6.0/timeout.rb:33:in `catch'
        from /usr/local/lib/ruby/2.6.0/timeout.rb:108:in `timeout'
        from /usr/local/bundle/gems/ssh_scan-0.0.41/lib/ssh_scan/client.rb:47:in `connect'
        from /usr/local/bundle/gems/ssh_scan-0.0.41/lib/ssh_scan/scan_engine.rb:75:in `scan_target'
        from /usr/local/bundle/gems/ssh_scan-0.0.41/lib/ssh_scan/scan_engine.rb:184:in `block (2 levels) in scan'

I found that client.rb appeared to be missing a rescue block for ENOPROTOOPT error codes. If I am mistaken on that please do tell ;)

Wanted to add tests for the change, but didn't find any in https://github.com/mozilla/ssh_scan/blob/master/spec/ssh_scan/client_spec.rb so I skipped it for now.

[claudijd]

@J12934 thanks! I'll cut a new gem release today to include this.