alpha-channel: Use stretch by default for k8s 1.11 on AWS
alpha-channel: Use stretch by default for k8s 1.11 on AWS

Jessie doesn't support NVME instances and this causes a lot of
confusion, as newer instances are NVME.

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