Comment 4 for bug 1413388

The culprit is the fix for https://bugs.launchpad.net/maas/+bug/1275649.

It creates a `edit_named_options` Django command that is run in postinst: that command is there to edit the named.conf.options file so that it includes the maas forwarders config. This command is supposed to parse the existing named.conf.options file and only add the required stanza but I suppose that this didn't work in your case.