rspamd spamfilter write loop for alias domain

There is an issue in 3.2.3 where server.php is stuck in a loop repeatedly creating a spamfilter file for an alias domain, which never completes.

To reproduce:

1. create a normal mail domain domainA.com with a spamfilter policy set
2. create an mail domain alias domainB.com to domainA.com, and do not set a spamfilter policy in domainB.com

The next run of server.sh will result in server.php looping. (Alternately, with the above scenario, edit the spamfilter policy of domainA.com so all entities with that filter are rewritten, and it will loop when it gets to domainB.com.)