Implement fact receiver thread worker

Optionally allow processing of fact receiver messages in a worker
thread.  This works around an issue where data could take a while to
page into Mongo and cross the zmq socket timeout.

awx/main/management/commands/run_fact_cache_receiver.py

@@ -3,6 +3,7 @@
 
 # Python
 import logging
+from threading import Thread
 from datetime import datetime
 
 # Django
@@ -76,14 +77,18 @@ class FactCacheReceiver(object):
             (fact_obj, version_obj) = Fact.add_fact(self.timestamp, facts, host, module)
             logger.info('Created new fact <fact, fact_version> <%s, %s>' % (fact_obj.id, version_obj.id))
 
-    def run_receiver(self):
+    def run_receiver(self, use_processing_threads=True):
         with Socket('fact_cache', 'r') as facts:
             for message in facts.listen():
                 if 'host' not in message or 'facts' not in message or 'date_key' not in message:
                     logger.warn('Received invalid message %s' % message)
                     continue
                 logger.info('Received message %s' % message)
-                self.process_fact_message(message)
+                if use_processing_threads:
+                    wt = Thread(target=self.process_fact_message, args=(message,))
+                    wt.start()
+                else:
+                    self.process_fact_message(message)
 
 class Command(NoArgsCommand):
     '''

awx/main/tests/commands/run_fact_cache_receiver.py

@@ -142,7 +142,7 @@ class RunFactCacheReceiverUnitTest(BaseTest, MongoDBRequired):
 
         receiver = FactCacheReceiver()
         receiver.process_fact_message = MagicMock(name='process_fact_message')
-        receiver.run_receiver()
+        receiver.run_receiver(use_processing_threads=False)
 
         receiver.process_fact_message.assert_called_once_with(TEST_MSG)