trex.common.services.trex_service_IPv6ND broken for some IPv6 VRRP implementations

[haklat43]

The TRex is looking in the wrong packet field when trying to interpret a NA received from GW. For at least some VRRP implementations the IPv6 src address in an NA is not same as the actual VRRP IPv6 address. IPv6 VRRP address in NA response should probably be filter on

scapy_pkt[ICMPv6ND_NA].tgt and not scapy_pkt[IPv6].src

Suggest following change in
automation/trex_control_plane/interactive/trex/common/services/trex_service_IPv6ND.py

In lookup function:
from:

    if ICMPv6ND_NA in scapy_pkt:
        return self.services.get((scapy_pkt[IPv6].dst, scapy_pkt[IPv6].src, tuple(vlans)), [] ) 

to:

    if ICMPv6ND_NA in scapy_pkt:
        return self.services.get((scapy_pkt[IPv6].dst, scapy_pkt[ICMPv6ND_NA].tgt, tuple(vlans)), [] )