SEARCH-665: Move connection/channel assignments (#122)

Fix "RuntimeError: maximum recursion depth exceeded in cmp" error.

It is assumed that sometimes acking a message fails, so the
`action_wrapper` decorator tries to reconnect to rabbitmq calling
`connect_to_rabbitmq` method, which re-does adding the callbacks,
then the new added callback fails, setting up a chain reaction.

See also https://chatlogs.metabrainz.org/libera/metabrainz/msg/4848594/

Co-authored-by: Michael Wiencek <mwtuea@gmail.com>

Author: amCap1712

sir/amqp/handler.py

@@ -196,8 +196,10 @@ def add_handler(queue, f, channel):
                 self.connection.close()
 
         conn = create_amqp_connection()
+        self.connection = conn
         logger.debug("Heartbeat value: %s" % conn.heartbeat)
         ch = conn.channel()
+        self.channel = ch
         # Keep in mind that `prefetch_size` is not supported by the version of RabbitMQ that
         # we are currently using (https://www.rabbitmq.com/specification.html).
         # Limits are requires because consumer connection might time out when receive buffer
@@ -207,8 +209,6 @@ def add_handler(queue, f, channel):
 
         add_handler("search.index", self.index_callback, ch)
         add_handler("search.delete", self.delete_callback, ch)
-        self.connection = conn
-        self.channel = ch
 
     @action_wrapper
     def requeue_message(self, msg, exc, fail=False):