This collects openstack cpu_util stats, grouped by hypervisor, and dumps
them into a JSON file.  The JSON file will be written into
/root/setup/cloudlab-openstack-stats.json . Currently it gets written
every 2 minutes (however, openstack by default collects CPU stats only
every 600 seconds...).

The format is quite simple. It's a dict of time periods -- currrently
the last 10 minutes, last hour, last 6 hours, last day, and last
week. Each period is also a dict, currently with two keys: vm_info and
cpu_util. vm_info contains a dict for each physical hypervisor node, and
that dict contains a mapping of openstack VM uuid to VM
shortname. cpu_util also contains a dict for each physical hypervisor
node, and that dict contains two keys: a total of the average cpu utils
for all the VMs on that node; and a "vms" dict containing the avg cpu
util for each VM.