Add one-shot mode
Add one-shot mode

Runs the monitor loop once, and reports which succeeded or not. Monitors
with "fail" in the name are expected to fail (for testing), and if they
don't (or if monitors which should succeed do not), exits non-zero.

jamesoff/simplemonitor,jamesoff/simplemonitor,jamesoff/simplemonitor,jamesoff/simplemonitor,jamesoff/simplemonitor