Relation lines disappear after commit

[Huw Wilkins]

For some bundles when you commit the changes the relation lines disappear.

To reproduce:
- search for "apache-hadoop-spark"
- drag the bundle to the canvas
- note that the relation lines appear
- deploy
- note that the relation lines have disappeared

It appears to be related to the bundle.yaml defintions.

Relations define in the following format will fail:

relations:
  - [yarn-master, hdfs-master]

Where as the following will succeed:

relations:
    - "gunicorn:wsgi-file"

[Huw Wilkins (huwshimi)]

For a working yaml see: http://bazaar.launchpad.net/~charmers/charms/bundles/django/bundle/view/head:/bundles.yaml

For a failing one see: http://bazaar.launchpad.net/~charmers/charms/bundles/apache-analytics-pig/bundle/view/head:/bundle.yaml