Comment 1 for bug 1660440

Since the rack and region can be run separately we'll need a warning for both. This can be checked as images are being imported on the region and the rack. But what constitutes low disk space? We could check the percentage of free disk space or base the number off the images we currently have.

Another idea I've had for awhile is to show the actual disk usage over the API and UI. But this has two issues
1. What happens when /var/lib/maas and /var/lib/postgresql are on different partitions?
2. Do we do this with an RPC call or roll and store the data?