etcd inventory

I fought with the `smartdc` python package for 20 minutes or so and couldn't get it to accept my private key, failing with `ValueError('Unsupport PEM encryption algorithm')` :rage4:.  Sync from Joyent is working for now with `sdc-listmachines` output fed into the thing like so:

``` bash
ansible-inventory-etcd sync-joyent -j <(sdc-listmachines)
```
Seems weird to have this script responsible for both just generating the inventory as well as syncing joyent inventory (the latter seems outside of what I would consider the responsibility). I'd be happy to see the joyent syncing be part of a separate file.