SSH config hostnames should be accepted as "address"

[kke]

For example, if you run vagrant boxes, you can do:

$ vagrant ssh-config core-02                                                                                    
Host core-02
  HostName 127.0.0.1
  User core
  Port 2200
  UserKnownHostsFile /dev/null
  StrictHostKeyChecking no
  PasswordAuthentication no
  IdentityFile /Users/kimmo/Projects/go/src/github.com/k0sproject/k0sctl/.vagrant/machines/core-02/virtualbox/private_key
  IdentitiesOnly yes
  LogLevel FATAL

If you put this into your ~/.ssh/config, it would be nice if you could do something like this in rig-using apps:

hosts:
  - ssh:
      address: core-02

As an alternative, something like this could be nice too:

hosts:
  - ssh:
      config: |
        Host core-02
        HostName 127.0.0.1
        User core
        Port 2200

[kke]

Solved in #145