[Reviewer: Mike] Poll bono and sprout using poll-sip

Mike,

Please can you review my changes to poll bono and sprout using poll-sip?  (Ben had already added `poll_bono.sh`/`poll_sprout.sh` placeholders.)  I've live-tested this running stably, detecting a hung bono, detecting a hung sprout and detecting a dead bono/sprout.  Obviously, there's no UT.

Matt