Initially, this patch ensured that the custom configuration
and readiness checks were applied after every restart of the
OVN North services. However, after removing the call that
triggered the restarting of the OVN/OVS services in [1],
this patch now serves as a refactor, separating the readiness
checks and custom configuration into a dedicated function.
[1] https://review.opendev.org/c/openstack/devstack/+/937606
Related-bug: #2091614
Related-bug: #2091019
Change-Id: Icba271292830204da94aa3353e93d52088d82eec
a976168235