isisd: fix crash on processing own p2p hello

isisd: fix crash on processing own p2p hello

isis_pdu.c :
isisd crashes if router's own p2p hello packets get processed
thereby creating an adjacecncy with itself. Asserts at
isis_find_vertex. So discard own p2p IIH PDU and avoid
creating adjacency with self. This would also fix duplicate
systemID on an interface. These checks already exists for IS-IS
LAN Level 1/2 Hello PDU in process_lan_hello, but not for
point-to-point IIH PDUs.

Signed-off-by: Amritha Nambiar <amritha.nambiar@intel.com>
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
(cherry picked from commit 491417ac6383e2ea557951b24eb7bd3fffb69394)