Change dns_send_question function arg from unicast to multicast

Change dns_send_question function arg from unicast to multicast

This trivial patch just reverses argument logic to make it a bit more
consistent with struct interface which contains "multicast" field. This
hopefully will make typos less likely and code easier to follow.

Signed-off-by: Rafał Miłecki <[email protected]>
Acked-by: John Crispin <[email protected]>