bgpd, topotests: bmp, fix wrong peer type for peer up/down events

bgpd, topotests: bmp, fix wrong peer type for peer up/down events

When running the bgp_bmp_2 vrf test, peer up/down events from the pre
and post policy are received with a wrong peer type value

> {"peer_type": "global instance", "policy": "pre-policy", "ipv6": false,
> "peer_ip": "192.168.0.2", "peer_distinguisher": "0:0", "peer_asn": 65502,
> "peer_bgp_id": "192.168.0.2", "timestamp": "2024-10-16 21:59:53.111962",
> "bmp_log_type": "peer up", "local_ip": "192.168.0.1", "local_port": 179,
> "remote_port": 50710, "seq": 4}

RFC7854 defines RD instance peer type, and later in 4.2 requests that
the peer distinguisher value be set to non zero value when the peer type
is not global. This is the case for peer vrf instances.

Fix this by modifying the BMP client, update the peer type
value by updating the peer type value when sending peer up/down messages.

Add a check in the bgp_bmp_2 test to ensure that peer type is correctly
set.

> {"peer_type": "route distinguisher instance", "policy": "pre-policy",
> "ipv6": true, "peer_ip": "192:168::2", "peer_distinguisher": "0:0",
> "peer_asn": 65502, "peer_bgp_id": "192.168.0.2", "timestamp":
> "2024-10-16 21:59:53.111962", "bmp_log_type": "peer up", "local_ip":
> "192:168::1", "local_port": 179, "remote_port": 50836, "seq": 5}

Signed-off-by: Philippe Guibert <philippe.guibert@6wind.com>