One checkpoint where the kext helper appears to work.
I'm still struggling with being able to replace the helper app
with a new version completely under program control.
Various changes to deal with the brokenness of SMJobBless around reinstalling
the helper app.  If it fails, we relaunch ourselves.  This seems to resolve the
problem always.  Also, since the launchd plist timeout doesn't seem to actually
kill the helper, a shutdown command was added.