Support N distributed agents

This is the third main feature of this system. The code needs a bunch of
polish, but it actually all works :)

I've tested this briefly with N <= 3.

Currently you have to build your own etcd cluster. It's quite easy, just
run `etcd` and it will be ready. I usually run it in a throw away /tmp/
dir so that I can blow away the stored data easily.

omv.yaml

@@ -1,7 +1,7 @@
 ---
 :domain: example.com
 :network: 192.168.123.0/24
-:image: centos-7.1
+:image: fedora-23
 :cpus: ''
 :memory: ''
 :disks: 0
@@ -34,5 +34,6 @@
 :reboot: false
 :unsafe: false
 :nested: false
+:tests: []
 :comment: ''
 :reallyrm: false