Cache metadata locally to allow conditional sync
Cache metadata locally to allow conditional sync

In isolation, updating the device metadata requires two API calls; one
to locate the device, and one to perform the update. Currently the API
libs take care of skipping the second call if nothing has changed,
however by caching locally we can also avoid the device lookup call.

serverdensity/chef-serverdensity,serverdensity/chef-serverdensity