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!