When finding nodes, we should bail on nodes without a proper hostname

[KAllan357]

Somehow, a Chef server can end up with improper Node objects.

For example, our server had:

Node Name:   node123
Environment: kyle_env
FQDN:
IP:
Run List:    recipe[cookbook::recipe]
Roles:
Recipes:
Platform:
Tags:

If the MB plugin is configured with the right groups, MB will find this node and attempt to operate on it. We should raise some sort of helpful error message "Hey, this node has no connectable information" and just ignore it. Or we could fail the whole run.

[KAllan357]

I guess technically, this code should be working, but maybe it is too strict.

https://github.com/RiotGames/motherbrain/blob/master/lib/mb/node_querier.rb#L127-L129

[capoferro]

As far as I understand, #present? is the same as !blank?, which means an empty string or nil should not pass the #present? check.