Comment 7 for bug 1113821

Alright, so I had a very quick look at the maintscript helper, and it won't help us in this case :(

So I think the best thing we can do is drop that rm from the postrm and move the restart of dnsmasq to the purge target.

This will be consistent with what any other similar package does, but has one drawback which is the thing I tried to avoid in the first place with the current implementation:
The file we ship in dnsmasq.d changes the way dnsmasq binds interfaces and I wanted to restore that behaviour without requiring a full purge of the rest of the config of the package. Sadly there's no easy way to do that without a lot of checksumming/preinst/postinst trickery which I'd rather avoid.

So the recommendation here is to just do that change in all 3 packages, SRU were applicable and tell people to use --purge if they want to restore dnsmasq's original behaviour.