[openstack] use NM to stop/start the interface
[openstack] use NM to stop/start the interface

The ifup/ifdown scripts are not available anymore in RHEL9
so use NM directly.
Rely on the availability of the old-style connection files.

Change-Id: Icd65e25c60f7d20db94226620ad70b80a200a477

redhat-openstack/infrared,redhat-openstack/infrared,redhat-openstack/infrared