We've been moving to try and separate several pieces of runqueue. Allow
start_worker to operate separately to rqexe since they don't need to be
tied. This allows rqexe to be available to print_diff for future
improvements.
(Bitbake rev: 834e452243ff2eea6e8e2e7f4935b5233ffb4b00)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>