[serverctl] fix db-dump
Since changeset af47954c1015 we would die with:
AttributeError: 'ServerMigrationHelper' object has no attribute 'repo'
# -*- coding: utf-8 -*-
# copyright %(year)s %(author)s, all rights reserved.
# contact %(author-web-site)s -- mailto:%(author-email)s
#
%(long-license)s
"""%(distname)s schema"""