spawn: use etcd3 with etcd-member.service
spawn: use etcd3 with etcd-member.service

As Bootkube and more generally Kubernetes will soon start using etcd3
by default, we need to start using etcd3 in the testing environment.
Because etcd3 is backward compatible with etcd2, any tested application
that currently use the etcd v2 API will continue to work as expected.

Reference: https://github.com/kubernetes-incubator/bootkube/pull/241
Reference: https://github.com/kubernetes/features/issues/44

marineam/mantle,glevand/coreos--mantle,dm0-/mantle,dm0-/mantle,quantum/coreos-mantle,marineam/mantle,glevand/coreos--mantle,quantum/coreos-mantle