this makes it possible to wait for the hook to exit in one place,
process its exit status for some purpose, and later process it in
another place for a different purpose. rpc will need this to shut
down a hook cleanly after the hook has completed its assignments.
Change-Id: I5af2d5aac4b02a0a200d720d0e6f0b5df5496aaf
eldritch horrors
6c416ff2ca