Comment 2 for bug 1381000

The way I think we should fix this is as follows:

 0. Have power drivers declare which tools they require in order to work.
 1. Have a periodic service running on the cluster which checks for the power
    management tools required by installed power drivers
 2. When the service runs and finds that a tool is missing, it reports the
    missing tool to the region.
 3. The region shows a warning:
    i. To admins.
    ii. Only if there are nodes that require the missing tool (so if you only
       have NUCs you won't get warnings about a missing ipmitool.
 4. When the service runs and finds all the tools it needs, it tells the
    region; the region can then cancel any outstanding warnings.

The only problem with this approach is that there'll be a lag between
installing the necessary packages and the warning going away.