report: adapt to changes in SpamAssassin DNS api

report: adapt to changes in SpamAssassin DNS api

SpamAssassin 4.0 changed the way it does DNS-lookups a bit (switched
to asynchronous lookups) - this broke pmg-system-report, since we use
the SpamAssassin API to check that DNS-resolution works.  The reason
for this is that SA used to take only the first entry from
/etc/resolv.conf - and SA being able to do correct resolution is
critical for it to work.

This patch fixes the incompatible use of the DNS-API, but does not
change to the asynchronous model.

Signed-off-by: Stoiko Ivanov <s.ivanov@proxmox.com>
Tested-by: Friedrich Weber <f.weber@proxmox.com>