celeryd: Use multiprocesing.freeze_support()

bin/celeryd

@@ -26,4 +26,6 @@ def main():
     celeryd.run_worker(**vars(options))
 
 if __name__ == "__main__":
+    import multiprocessing
+    multiprocessing.freeze_support()
     main()

celery/bin/celeryd.py

@@ -420,6 +420,7 @@ def run_worker(**options):
 
 
 def main():
+    multiprocessing.freeze_support()
     options = parse_options(sys.argv[1:])
     return run_worker(**vars(options))