Link discovery provider is getting egress links that to determine the which links are added or removed now.
But LLDP packet is received from remote device.
It means that link detection is guaranteed by ingress direction.
So, link discovery provider should get the links from ingress direction by each device.
[Remote Device ---(Egress)--(LLDP packets flow)--(Ingress)---> My Device]
ONOS-7749
Change-Id: Ie77d0ad37f2afb1cdea0cc3f55c366836097db87