Bug#789247: di-netboot-assistant: broken deb.d.o urls

[Matt Taggart <taggart@debian.org>]

It looks like the deb.debian.org URLs in di-sources.list need to be updated

E: Can't download 'stretch' for 'amd64' 
(http://deb.debian.org/dists/stretch/main/installer-amd64/current/images/MD5SUMS).

The URL should have a leading 'debian/' in the path, ie

http://deb.debian.org/dists/stretch/main/installer...

I don't know if this is just some mirrors or everywhere, but not having 
it resulted in an error for me (it resolved to cdn-aws.deb.debian.org)

Thanks,

--
Matt Taggart
taggart@debian.org