Fix Add-on Domain Masking

Not sure if I'm describing it correctly, but we did a migration from another server where lets say; site1.com was the main hosted account, which had addon1.com as a add-on domain which was just a shorter spelling of the main domain. However now it's directing the add-on domain to the subdomain which actually just points to the public_html folder anyways. So it's basically changing addon1.com to addon1.site1.com which is really just site1.com public_html folder anyways. So it seems something got lost in the translation, the domain is functioning and resolving to the right spot, however it's just no longer properly "masking" it.