run-as-hook needs to require the target unit agent to be local

[Clint Byrum]

There is some concern that a destructive script might be run using 'jitsu run-as-hook'. Something like this:

rm -rf `jitsu run-as-hook data-service/1 config-get my-service-data-dir`

And then if that is run on your local machine it might end up wiping out / because data-service/1 says its on / on its cloud node, but you are running it on your client.

We should verify that the local unit agent is available before letting this run. That would at least keep this problem from happening.