enqueue_dependents now uses origin queue to enqueue

Current implementation is using the first job queue
to insert the dependent jobs. This makes RQ to ignore
the original queue where the jobs were enqueued.

With this change, we will use job origin attribute to
fetch the original queue, then insert the dependent
job to the fetched queue.

fixes issue #512

rq/queue.py

@@ -289,15 +289,22 @@ class Queue(object):
         # TODO: can probably be pipelined
         from .registry import DeferredJobRegistry
 
-        registry = DeferredJobRegistry(self.name, self.connection)
+
 
         while True:
             job_id = as_text(self.connection.spop(job.dependents_key))
             if job_id is None:
                 break
             dependent = self.job_class.fetch(job_id, connection=self.connection)
-            registry.remove(dependent)
-            self.enqueue_job(dependent)
+            registry = DeferredJobRegistry(dependent.origin, self.connection)
+            with self.connection._pipeline() as pipeline:
+                registry.remove(dependent, pipeline=pipeline)
+                if dependent.origin == self.name:
+                    self.enqueue_job(dependent)
+                else:
+                    queue = Queue(name=dependent.origin, connection=self.connection)
+                    queue.enqueue_job(dependent)
+                pipeline.execute()
 
     def pop_job_id(self):
         """Pops a given job ID from this Redis queue."""