ephemeral-disk-warning.service causes ordering cycle on multi-user.target

=== Begin SRU Template ===
[Impact]
Some recent systemd related cloud-init changes in 0.7.7-28-g34a26f7-0ubuntu1
and later caused systemd 'ordering cycle' around the walinuxagent provided
ephemeral-disk-warning.service .

The result would be that journalctl would report:
   Breaking ordering cycle by deleting job ephemeral-disk-warning.service/start
Due to a order cycle

 * An explanation of the effects of the bug on users and

 * justification for backporting the fix to the stable release.

 * In addition, it is helpful, but not required, to include an
   explanation of how the upload fixes this bug.

[Test Case]
Boot system on azure, then run:

$ journalctl | grep -i "ordering cycle"

There *should* be no ordering cycles in our boot.

$ systemctl status ephemeral-disk-warning.service | grep Condition
Condition: start condition failed at Tue 2016-09-20 16:15:03 UTC; 37min ago

That is the failure, to show it functional and fixed

$ echo "deb http://archive.ubuntu.com/ubuntu $(lsb_release -sc)-proposed main" |
   sudo tee /etc/apt/sources.list.d/proposed.list
$ sudo apt-get update -qy
$ sudo apt-get -qy install walinuxagent
$ dpkg-query --show walinuxagent
$ sudo reboot

Then repeat the above, and you should see no 'ordering cycle' messages, and

$ systemctl status ephemeral-disk-warning.service | grep Active
   Active: active (exited) since Tue 2016-09-20 17:08:46 UTC; 1h 0min ago

And the file that gets created should be there.
$ ls -l /mnt/DATALOSS_WARNING_README.txt
-r--r--r-- 1 root root 639 Sep 20 17:08 /mnt/DATALOSS_WARNING_README.txt

[Regression Potential]
Changing order of boot is quite often painful due to subtle changes and
the overall newness of systemd. The changes here are fairly well tested
and fix an issue. Worst case, that job does not run (as it does not run now)
and we do not get the file created.

[Other Info]
This is fallout of fix for bug 1576692.
Full description of the fix is:
    debian/ephemeral-disk-warning.service: avoid systemd ordering cycle

    ephemeral-disk-warning.service had 'WantedBy' of multi-user.target
    which implies "Before" of multi-user.target. It also had
    After of cloud-final.service. Since cloud-final.service is now
    After multi-user.target, that caused the cycle.

    Relax this to be only After cloud-config.service which will run
    before multi-user.target does and avoid the cycle.

    Also add a 'Description'.

    LP: #1624596
--- End SRU Template ---

$ journalctl | grep break -a2 -b8
42956-Sep 17 01:45:02 smoser0917x systemd[1]: Detected virtualization microsoft.
43031-Sep 17 01:45:02 smoser0917x systemd[1]: Detected architecture x86-64.
43101-Sep 17 01:45:02 smoser0917x systemd[1]: Set hostname to <smoser0917x>.
43172-Sep 17 01:45:02 smoser0917x systemd[1]: multi-user.target: Found ordering cycle on multi-user.target/start
43279-Sep 17 01:45:02 smoser0917x systemd[1]: multi-user.target: Found dependency on ephemeral-disk-warning.service/start
43395-Sep 17 01:45:02 smoser0917x systemd[1]: multi-user.target: Found dependency on cloud-final.service/start
43500-Sep 17 01:45:02 smoser0917x systemd[1]: multi-user.target: Found dependency on multi-user.target/start
43603-Sep 17 01:45:02 smoser0917x systemd[1]: multi-user.target: Breaking ordering cycle by deleting job ephemeral-disk-warning.service/start
43739:Sep 17 01:45:02 smoser0917x systemd[1]: ephemeral-disk-warning.service: Job ephemeral-disk-warning.service/start deleted to break ordering cycle starting with multi-user.target/start
43922-Sep 17 01:45:02 smoser0917x systemd[1]: Listening on udev Kernel Socket.
43995-Sep 17 01:45:02 smoser0917x systemd[1]: Reached target Encrypted Volumes.
44069-Sep 17 01:45:02 smoser0917x systemd[1]: Listening on Syslog Socket.
44137-Sep 17 01:45:02 smoser0917x systemd[1]: Started Forward Password Requests to Wall Directory Watch.
44236-Sep 17 01:45:02 smoser0917x systemd[1]: Listening on Journal Socket.
44305-Sep 17 01:45:02 smoser0917x systemd[1]: Listening on LVM2 poll daemon socket.
44383-Sep 17 01:45:02 smoser0917x systemd[1]: Reached target Swap.
44444-Sep 17 01:45:02 smoser0917x systemd[1]: Listening on fsck to fsckd communication Socket.

$ dpkg-query --show cloud-init walinuxagent
cloud-init 0.7.8-1-g3705bb5-0ubuntu1~16.04.1
walinuxagent 2.1.3-0ubuntu4.1

Related bugs:
 * bug 1576692: fully support package installation in systemd

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: walinuxagent 2.1.3-0ubuntu4.1
ProcVersionSignature: User Name 4.4.0-36.55-generic 4.4.16
Uname: Linux 4.4.0-36-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.1
Architecture: amd64
Date: Sat Sep 17 01:51:22 2016
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: walinuxagent
UpgradeStatus: No upgrade log present (probably fresh install)