machine-type generator: Warn if instance type not in ENI map
machine-type generator: Warn if instance type not in ENI map

And we write these warnings to the output, so that we can see them in
PR review.

gambol99/kops,aledbf/kops,gambol99/kops,kubernetes/kops,blakebarnett/kops,gambol99/kops,kubernetes/kops,aledbf/kops,robinpercy/kops,aledbf/kops,robinpercy/kops,gambol99/kops,blakebarnett/kops,justinsb/kops,justinsb/kops,justinsb/kops,robinpercy/kops,robinpercy/kops,aledbf/kops,blakebarnett/kops,kubernetes/kops,blakebarnett/kops