Fix OVN leader detection in chassis priority fix

[bbezak]

After kolla-ansible patch [1] ovn commands can run on all nodes. Changing method of getting the leader.

[1] https://review.opendev.org/c/openstack/kolla-ansible/+/963412

error in previous method - multiple "leaders":

TASK [Assert one leader exists] ***************************************************************************************************************************************************************************************************
Tuesday 04 November 2025  20:19:54 +0000 (0:00:00.024)       0:00:06.813 ******
fatal: [HOST1]: FAILED! =>
    assertion: groups['ovn_nb_leader'] | default([]) | length == 1
    changed: false
    evaluated_to: false
    msg: 'Expected exactly 1 OVN NB leader, but found 4: [''''HOST1'', ''HOST2',
        ''HOST3'', ''HOST4'']'
fatal: [HOST2]: FAILED! =>
    assertion: groups['ovn_nb_leader'] | default([]) | length == 1
    changed: false
    evaluated_to: false
    msg: 'Expected exactly 1 OVN NB leader, but found 4: [''HOST1'', ''HOST2',
        ''HOST3'', ''HOST4''']'
fatal: [HOST3]: FAILED! =>
    assertion: groups['ovn_nb_leader'] | default([]) | length == 1
    changed: false
    evaluated_to: false
    msg: 'Expected exactly 1 OVN NB leader, but found 4: ['''HOST1'', ''HOST2',
        ''HOST3'', ''HOST4'']'
fatal: [HOST4]: FAILED! =>
    assertion: groups['ovn_nb_leader'] | default([]) | length == 1
    changed: false
    evaluated_to: false
    msg: 'Expected exactly 1 OVN NB leader, but found 4: [''HOST1'', ''HOST2',
        ''HOST3'', ''HOST4'']'

[gemini-code-assist]

Code Review

This pull request addresses a bug in OVN leader detection within the chassis priority fix playbook. The previous method, which relied on the exit code of ovn-nbctl get-connection, became unreliable after a related change, leading to multiple nodes being identified as leaders. The fix replaces this with a more robust method using ovs-appctl cluster/status and checking the output for the node's role. This change is correct and effectively resolves the issue. I have one minor suggestion to improve the code's readability and maintainability.