Add RQ_QUEUES to default config

We can use string interpolation in the file rather than building it when
making the config. Adding the value to the config allows us to override
it with an environment variable, if we want to (as we do for the UAT
environment).

atst/app.py

@@ -102,7 +102,7 @@ def map_config(config):
         ),
         "REQUIRE_CRLS": config.getboolean("default", "REQUIRE_CRLS"),
         "RQ_REDIS_URL": config["default"]["REDIS_URI"],
-        "RQ_QUEUES": ["atat_{}".format(ENV.lower())],
+        "RQ_QUEUES": [config["default"]["RQ_QUEUES"]],
     }