upgrade 1.14.1 to 1.16.2 leaves machine agents not upgraded

[James Sapara]

Running on EC2 with a small instance.

Ran the following command this morning: juju upgrade-juju
No errors reported on console after running

All the nodes are down, but services are otherwise running normally.

I would expect all services to restart with the new 1.16.2 symlinked agent and status to be started after a small time.

`juju status` http://pastebin.com/H0jc3zs6

machine-0 info:
machine-0.log from that time: http://pastebin.com/QuLFM3hq
machine agent is linked to 1.14.1 tools, but has 1.16.2 downloaded
```
ubuntu@ip-x-x-x-x:/var/lib/juju/tools$ ls -la
total 16
drwxr-xr-x 4 root root 4096 Nov 4 22:06 .
drwxr-xr-x 5 root root 4096 Sep 24 15:18 ..
drwxr-xr-x 2 root root 4096 Sep 24 15:17 1.14.1-precise-amd64
drwx------ 2 root root 4096 Nov 4 22:16 1.16.2-precise-amd64
lrwxrwxrwx 1 root root 20 Sep 24 15:19 machine-0 -> 1.14.1-precise-amd64
```

Machine-2 information:

upstart job for agent: http://pastebin.com/qEKMk3hK
log from time of upgrade-juju: http://pastebin.com/3dTCS9W1
unit on the machine is using the 1.16.2 tools, the machine agent is using the old 1.14.1 tools
```
ubuntu@ip-x-x-x-x:/var/lib/juju/tools$ ls -la
total 16
drwxr-xr-x 4 root root 4096 Nov 4 22:04 .
drwxr-xr-x 5 root root 4096 Sep 24 16:14 ..
drwxr-xr-x 2 root root 4096 Sep 24 16:14 1.14.1-precise-amd64
drwx------ 2 root root 4096 Nov 4 22:04 1.16.2-precise-amd64
lrwxrwxrwx 1 root root 20 Sep 24 16:14 machine-2 -> 1.14.1-precise-amd64
lrwxrwxrwx 1 root root 20 Nov 4 22:04 unit-picatic-api-0 -> 1.16.2-precise-amd64
```

[James Sapara (james-sapara)]

Would appreciate any thoughts on how to bring these node agents back online. This is currently sitting on our production cluster, cloning and redeploying is an option, but would like to see if we can get this one rolling again.

[James Sapara (james-sapara)]

Preformed the following command in `/var/lib/juju/tools` on machine-0:

`rm machine-0 && ln -s 1.16.2-precise-amd64 machine-0`

A `juju status` immediately after showed all node agents back and running 1.16.2.

[Curtis Hovey (sinzui)]

The Juju-ci saw this happen going from 1.18.0 to 1.18.2