faulty external user repository connection causes EMPTY user and group lists

If ldap is enabled in atlassian-user.xml but the connection is faulty :

• Users can still log in (if they have a local account and group membership)
• The admin > Users and > Group lists are empty
• Searching for a user works and the (local) user is is found.

Bamboo should reliably fall back to the local repository content in case the external one become unavailable.