Kops: Allow opt-in to etcd3

[justinsb]

If etcd3 in 1.6 continues to look like a "go" on GCE, we should allow kops users to opt-in (we probably should let people opt-in anyway, but we might need an "IAmDoingThisAtMyOwnRisk" FeatureFlag!)

One option is to do the same thing we do for networking:

storage:
  etcd2: {}

and

storage:
  etcd3: {}

This would also allow further customization in future - for example running with encryption etc.

[chrislovecnm]

So how the heck do we upgrade :) 🙊

[mad01]

One option can be to add a opt in to create with etcd3 and leave upgrade unsupported as a start to allow new cluster to be created with etcd3.

what is your veiw of that?

[zioalex]

I like this idea and looking how to migrate to etcd3 . Any concrete plan here?

[chrislovecnm]

We have this in place now