OutOfMemoryError during reindex all (due to EagerLoadingOfbizCustomFieldPersister's caching of custom field values)

The EagerLoadingOfbizCustomFieldPersister is storing an Issue's custom field values in a ThreadLocal so a request may access the same values in a timely manner if requested again. Unfortunately a reindex all process touches every issue, slowly building these caches up and not releasing until either the reindex thread pool is discarded and the threads die or an OutOfMemoryError occurs. We should really SoftReference the list of values.