ospfd: ospf nbr in full although mismatch in hello packet contents

ospfd: ospf nbr in full although mismatch in hello packet contents

Issue:
===================
OSPF neighbors are not going down even after 10 mins when
having a mismatch in hello and dead interval.
First neighbors are formed and then a mismatch in the interval
is created, it is observed that the neighbor is not going down.

Root Cause Analysis:
====================
The event HelloReceived defined in RFC 2328 was named as PacketReceived
and this event was scheduled whenever LS Update, LS Ack, LS Request,
DD description packet or Hello packet is received.
Although there is a mismatch in the Hello packet contents, the
event PacketReceived gets triggered due to LS Update received and the
dead timer gets reset and hence the neighbor was never going Down and
remains FULL.

Fix:
==================
As per RFC 2328, the HelloReceived needs to be triggered only when
valid OSPF Hello packet is received and not when other OSPF packets
are received. Modified the function name as well.

Signed-off-by: Mobashshera Rasool <mrasool@vmware.com>