Disable unforked interval runs.

:construction: WIP

@lamont-granquist Right track so far?
you might want to mention that interval sleeps are moved to the top of the loop now so that chef will sleep before running instead of running and then sleeping.

also you've got the fix so that SIGTERM will cause the daemonized looper to exit immediately while maintaining the SIGTERM behavior in the converging client of doing a graceful exit.