apply max path config during early networking

[internet-diglett]

Summary

When mgd starts up it has a default "bestpath fanout" value of 1. We added the ability to configure this to other values in R18, and nexus does configure it once it's up and running, but we didn't add the call to configure it during early networking. While ECMP isn't critical during the early networking phase, it makes sense to keep the environment consistent throughout the various phases of operation.

Testing

With the following bgp config:

[[rack_network_config.bgp]]
asn = 47
max_paths = 2
originate = [ "198.51.100.0/24" ]

[[rack_network_config.bgp]]
asn = 47
max_paths = 2
originate = [ "198.51.100.0/24" ]

Verified in a4x2 that the mgd daemon reports a fanout value of 2 before nexus is online:

root@oxz_switch:~# mgadm rib fanout read
2
root@oxz_switch:~#
logout

[Connection to zone 'oxz_switch' pts/1 closed]
root@g0:~# zoneadm list
global
oxz_switch
oxz_internal_dns_e441c492-4db2-4597-937e-9727d6fe80a3
oxz_ntp_bf7fbe3a-68cd-4a0e-80db-d031ee470670
root@g0:~#

main currently shows 1:

root@g0:~# zoneadm list
global
oxz_switch
oxz_internal_dns_19d89acf-98de-447c-83fe-9d25c97f42cb
oxz_ntp_b8269b78-24b2-4157-8fbd-ca75fba70edb
root@g0:~# zlogin oxz_switch
[Connected to zone 'oxz_switch' pts/1]
Last login: Tue Mar  3 03:16:13 on pts/1
The illumos Project     helios-2.0.23759        February 2026
-bash: /opt/ooce/bin/jq: No such file or directory
root@oxz_switch:~# mgadm rib fanout read
1