etcd: put etcd inside of containers

[philips]

For historical reasons we have had to create /usr/bin/etcd and /usr/bin/etcd2 which has two problems:

• It is confusing
• It adds to the size of CoreOS images

We can fix this. Here is a design doc for how we put etcd v3.0 inside of containers while providing a similar UX to what exists today: https://docs.google.com/document/d/1W0vqVctpxpALhOyyZAHaYEPKukGSQOf_L_B3Qx_NR9w/edit#

[steveej]

With coreos/coreos-overlay#2015 merged we now have the app-emulation/etcd-wrapper which implements phase 1 of the linked document. Where should the documentation go for this?

[crawford]

Fixed with coreos/coreos-overlay#2068.