arp(8): fixing the deletion failure of IEEE1394 associated addresses

Without this, 'arp -d ${IEEE1394_ADDRESS}' gives the following error:

arp: delete: cannot locate 10.0.0.71

Reviewed by: glebius
MFC after: 2 weeks

(cherry picked from commit a0d6d0d0b9aba6d4c025b2f2807e7c4b4c4b2415)