Add docs that debian 9 images should work
Add docs that debian 9 images should work

gambol99/kops,justinsb/kops,andrewsykim/kops,gambol99/kops,chrislovecnm/kops,kubernetes/kops,mad01/kops,andrewsykim/kops,kubernetes/kops,robinpercy/kops,blakebarnett/kops,andrewsykim/kops,tsupertramp/kops,robinpercy/kops,blakebarnett/kops,tsupertramp/kops,justinsb/kops,gambol99/kops,aledbf/kops,tsupertramp/kops,andrewsykim/kops,aledbf/kops,chrislovecnm/kops,blakebarnett/kops,pdh/kops,mad01/kops,robinpercy/kops,robinpercy/kops,pdh/kops,kubernetes/kops,chrislovecnm/kops,pdh/kops,tsupertramp/kops,justinsb/kops,mad01/kops,aledbf/kops,aledbf/kops,chrislovecnm/kops,mad01/kops,gambol99/kops,pdh/kops,blakebarnett/kops