Comment 11 for bug 1616861

MDNS authorities don't reply to every request. They may delay
responses and may not reply if the same query is carried out after
a very short time. This happens in hplip because the same queries
are issued during startup repeatedly.

This can be solved easily by retrying the query after a a short
wait. Typically in my environment queries will reliably succeed after
500ms for single lookups and 1000ms for scanner lookups.

The logic is the same for both normal fqdn lookup and scanner query,
so put it in a separate function.