ISSUE:

ISSUE:
LSAcks (for directed acks) are being sent to neighbor's unicast address.

RFC 2328 says:

"The IP destination address for the packet is selected as
 follows.  On physical point-to-point networks, the IP
 destination is always set to the address AllSPFRouters"

Fix is to unconditionally set the destination address for LSAcks over
point-to-point links as AllSPFRouters. Quagga OSPF already has similar
change for OSPF DBD, LSUpdate and LSrequest packets.

Signed-off-by: Vipin Kumar <vipin@cumulusnetworks.com>
Reviewed-by: Daniel Walton <dwalton@cumulusnetworks.com>
Reviewed-by: Dinesh G Dutt <ddutt@cumulusnetworks.com>