[ARP]: Move inet_addr_type call after simple error checks in arp_contructor.

The neighbour entry will be destroyed in the case of error, so it is
pointless to perform constly routing table lookup in this case.

Signed-off-by: Denis V. Lunev <den@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>