bitbake: cooker: gracefully shutdown parsers

CookerParser.shutdown code doesn't do all required work to shutdown
parser processes. As a result bitbake hangs if interrupted during
parsing. Putting None into the parser_quit queue should fix this issue
as it makes parsers to quit main loop.

(Bitbake rev: f67307977e8f089ce6d208d3e9de2a6a1768757e)

Signed-off-by: Ed Bartosh <ed.bartosh@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/cooker.py

@@ -2058,6 +2058,7 @@ class CookerParser(object):
             self.feeder_quit.put(None)
             for process in self.processes:
                 self.jobs.put(None)
+                self.parser_quit.put(None)
         else:
             self.feeder_quit.put('cancel')