queue: Use normal instance data in SimpleQueue

Code like this is dangerous:

    class SimpleQueue(object):
        queues = set()

because all instances will share the same 'queues' set object.

We don't really need multiple instances, but neither is there a reason to break
them.  So do the normal Python thing instead.

(imported from commit a56bb8414dd549cfd312c9565df198cf9d20f08a)

zephyr/lib/queue.py

@@ -7,13 +7,11 @@ import simplejson
 # interface for external files to put things into queues and take them
 # out from bots without having to import pika code all over our codebase.
 class SimpleQueueClient(object):
-    connection = None
-    channel = None
-    queues = set()
-    _inited = False
-
     def __init__(self):
-        pass
+        self.connection = None
+        self.channel = None
+        self.queues = set()
+        self._inited = False
 
     def initialize(self):
         # Initialize the connection