bind9 systemd related problems

[Nikolay Shaplov]

For many cases (IPv4 only recursor) bind9 should be started with -4 option.

The common way to do this in debian was to add -4 to an OPTIONS in  
/etc/default/bind9

but current systemd harness do ignore /etc/default/bind9 and there is no way 
to start bind9 with -4 flag.

This issue is described in a bug
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=767798

But bind9 maintainers seems to ignore it. And it is important one.

So I would like to ask you, to encourage them to fix the bug, or do non-
maintainer upload or something. 

Cause this bug affects a lot of cases and there is no way to solve it without 
touching /lib/systemd/system/bind9.service and it is not nice way at all...