Without explicitly joining the thread, it's possible for the process to end
(e.g. after a bitbake -p) and kill off the thread without waiting for it to
exit cleanly. So, register the thread join with atexit.
(Bitbake rev: 97ce57e6f860d3e6f34cc7a603ed1eeac4f423d3)
Signed-off-by: Chris Larson <chris_larson@mentor.com>
Signed-off-by: Richard Purdie <rpurdie@linux.intel.com>