bgpd: Relax peer to be on the same host

bgpd: Relax peer to be on the same host

If the existing listener is the same as the peer, treat as self and reject.

```
exit1-debian-11# sh bgp listeners
Name             fd Address
---------------------------
default          24 192.168.10.123
exit1-debian-11# con
exit1-debian-11(config)# router bgp
exit1-debian-11(config-router)# neighbor 192.168.10.123 remote-as external
% Can not configure the local system as neighbor

exit1-debian-11# sh bgp listeners
Name             fd Address
---------------------------
default          24 0.0.0.0
default          25 ::
exit1-debian-11# con
exit1-debian-11(config)# router bgp
exit1-debian-11(config-router)# neighbor 192.168.10.123 remote-as external
% Can not configure the local system as neighbor
exit1-debian-11(config-router)#

exit1-debian-11# sh bgp listeners
Name             fd Address
---------------------------
default          24 192.168.0.1
exit1-debian-11# con
exit1-debian-11(config)# router bgp
exit1-debian-11(config-router)# neighbor 192.168.10.123 remote-as external
exit1-debian-11(config-router)#
```

Signed-off-by: Donatas Abraitis <donatas.abraitis@gmail.com>