list of previously prepared releases should not depend on build agent state

Steps to reproduce:

1. prepare a release, but don't click "Done"
2. restart the continuum build agent that performed the release
3. Click done (or go to the project page and press release again)

Note that the prepared release is not present. This is a result of the agent no longer having in its memory the previous releases.

Likewise, if the agent remains down you will receive an errors message.

This is unnecessary just to determine the name, which is already in the release model. It should be possible perform a release on a different agent, using the existing configuration.