sdc-thoth should install itself on new CNs

[bcantrill]

No description provided.

[elijah]

It would be great if thoth were more like one of the existing agents. I don't see any real reason it couldn't just be included in those installers/updaters, unless you have philosophical objections to having a thing-that-runs-from-cron be distributed like an agent that's always-on. :)

[jussisallinen]

If thoth would be installed as agent it could be handled through sdcadm post-setup and updated just like ie. cmon-agent, dockerlogger etc. is updated.

Sure this isn't top priority thing to go do but it would make thoth more in line with all the other pieces of sdc/triton.

Installing to new CN's could be just as with dockerlogger (taken from https://github.com/joyent/sdc-docker#installation)

# sdcadm update thoth --servers ${CN1},${CN2},...