Handle peer relation for missing services.

    QA:
    - juju-quickstart the GUI in a local env;
    - juju set juju-gui juju-gui-console-enabled=true
    - deploy wordpress from the JS console:
      app.env.deploy('cs:precise/wordpress-21', 'wordpress', null, null, 1, null);
      You should see a "Relation added without matching service" error;
    - destroy the wordpress service using the GUI inspector;
    - now switch to this branch:
      juju set juju-gui juju-gui-source="https://github.com/frankban/juju-gui.git reorder-delta";
    - wait for the GUI to be ready again, this takes a while;
    - reload the GUI (CTRL-SHIFT-R);
    - deploy wordpress from the JS console:
      app.env.deploy('cs:precise/wordpress-21', 'wordpress', null, null, 1, null);
      You should see a "relation change wordpress:loadbalancer delayed"
      log message, and the wordpress relation tab should show the peer relation;
    - done, destroy your environment, thank you!