LDAP/Crowd Users auto-synced and added as crucible users, exceeding licence limit

When a new user is synced for LDAP or Crowd (possibly also when auto-adding), it is automatically enabled for FishEye and Crucible.

This makes it possible that the users license limit is exceeded, meaning that all attempts to use FishEye and Crucible thereafter redirect to the user admin page (CRUC-5927)

We need to improve this, to not add users that would exceed the license limits and instead log messages saying we are not adding them.