cloud-init: Remove importing DNS settings

cloud-init: Remove importing DNS settings

Those scripts used to import settings from the meta-data services
and wrote them to the local configuration files.

For the DNS settings and Amazon, this is no longer possible because
their DNS servers do not support DNSSEC at all. Therefore we default
to recursor mode.

To be consistent across cloud providers, we are doing the same for
Azure.

Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>
Signed-off-by: Arne Fitzenreiter <arne_f@ipfire.org>