net: dns: Set the address family and address length correctly

We need to set the resolved IP address family and length
before calling the user callback so that callback does not
need to figure out these values itself.

Change-Id: I724909fc1707608ab8728231a0311795b6a313f3
Signed-off-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>