Comment 5 for bug 1693582

Validated spinning up GCE instances xenial yakkety and zesty and performing the following operations:
---- xenial
$ sudo cat /etc/apt/sources.list.d/1.list
deb http://archive.ubuntu.com/ubuntu/ xenial-proposed main

$ sudo apt update
# sudo apt install cloud-init
$ sudo reboot
$ sudo cloud-init single --name cc_ssh --frequency always
Cloud-init v. 0.7.9 running 'single' at Fri, 16 Jun 2017 21:08:36 +0000. Up 142.47 seconds.
Generating public/private rsa key pair.
...

$ sudo grep csmith /home/ubuntu/.ssh/authorized_keys
ssh-rsa AAAAB3NzaC1yc2E....GoOB csmith@fringe

$dpkg-query --show cloud-init
      0.7.9-153-g16a7302f-0ubuntu1~16.04.1cloud-init

--- yakkety
$ sudo cat /etc/apt/sources.list.d/1.list
deb http://archive.ubuntu.com/ubuntu/ yaketty-proposed main

$ sudo apt update
# sudo apt install cloud-init
$ sudo reboot
$ sudo cloud-init single --name cc_ssh --frequency always
...
blackboxsw@instance-1:~$ sudo grep csmith /home/ubuntu/.ssh/authorized_keys
ssh-rsa AAAAB3...NGoOB csmith@fringe
blackboxsw@instance-1:~$ dpkg-query --show cloud-init
cloud-init 0.7.9-153-g16a7302f-0ubuntu1~16.10.1

---- zesty

$ sudo cat /etc/apt/sources.list.d/1.list
deb http://archive.ubuntu.com/ubuntu/ zesty-proposed main

$ sudo apt update
# sudo apt install cloud-init
$ sudo reboot
$ sudo cloud-init single --name cc_ssh --frequency always
$ sudo grep csmith /home/ubuntu/.ssh/authorized_keys
ssh-rsa AAAAB3Nz...xNGoOB csmith@fringe
$ dpkg-query --show cloud-init
cloud-init 0.7.9-153-g16a7302f-0ubuntu1~17.04.1