Change MX entries back on domain deletion

[lucasRolff]

Version information

Latest

Steps to replicate

1. Have a cPanel account running via SpamExperts
2. Delete the account with "Keep DNS Zone" enabled (this assumes you migrated the domain to another server)
3. See SpamExperts happily deleting the domain without changing back the MX

Actual result

SpamExperts doesn't try to revert the MX settings when deleting a domain from the cluster (within the cPanel plugin), this happens in case you e.g. delete an account that you've transferred to another server.
You'll end up with a DNS zone going to SpamExperts, but SpamExperts returning "relay not permitted" due to the domain not being configured on the cluster anymore.

Expected result

Even when you delete a domain, before deleting it, change MX back to original - just assume that the zone might not actually get deleted afterwards

Other notes