Return connection parameters from Pika/Stomp plugin activation

This means that the parameters are available on the configuration object,
rather than having to go via the expected transport every time.

Author: ndevenish

src/workflows/util/zocalo/configuration.py

@@ -48,6 +48,7 @@ def activate(configuration):
             ("prefix", "--stomp-prfx"),
         ]:
             StompTransport.defaults[target] = configuration[cfgoption]
+        return dict(StompTransport.defaults)
 
 
 class Pika:
@@ -70,6 +71,7 @@ def activate(configuration):
             ("vhost", "--rabbit-vhost"),
         ]:
             PikaTransport.defaults[target] = configuration[cfgoption]
+        return dict(PikaTransport.defaults)
 
 
 class DefaultTransport: