ipdevpoll should be able to perform reverse DNS lookups using /etc/hosts file

[lunkwill42]

Some users insist on wanting names on their devices, yet refuse to use DNS to actually register these names. They attempt to add entries in the NAV server's /etc/hosts file instead, but find that while SeedDB will happily accept this when performing reverse lookups, ipdevpoll will not - because ipdevpoll will only use the DNS resolvers mentioned in /etc/resolv.conf.

This should be easily mitigated through more canonical uses of the Twisted names framework that ipdevpoll employs for DNS lookups.