Some entries in data/virtual-mailman can be duplicates or be missing VIRTUAL_MAILMAN_LOCAL_DOMAIN

[Mark Sapiro]

If VIRTUAL_MAILMAN_LOCAL_DOMAIN is non-empty it should also be appended to the addresses in the SITE ADDRESSES stanza.

If the site list's host_name attribute is in POSTFIX_STYLE_VIRTUAL_DOMAINS the site list posting address will be in both the SITE ADDRESSES stanza an in the list's virtual mapping stanza. This causes postmap to warn about the duplication.