Updating a DNS zone in Webmin fails to run rndc (zone) reload on webmin dns slaves.

Per this forum thread:

http://www.virtualmin.com/forums/virtualmin/getting-dns-updates-to-updat...

If I simply make a change in Webmin, and then apply it, the zone gets updated locally on that box, but it does not update until the TTL expires on the slave servers. If I manually run rndc (zone) reload on the slaves, they get the update just fine.