With the netcf backend (RHEL/AlmaLinux 8), undefining a bridge also
removes its members' configuration: the device came back without any
after a reboot. Like virsh iface-unbridge, each member is now defined
again on its own after the bridge is undefined, with the bridge's start
mode and, when it is the only member, its addresses. A bond keeps its
mode and devices.
Checked on AlmaLinux 8 (libvirt 8.0, netcf): an ethernet and a bond
member get their ifcfg back, and the bond comes up with the address
after a reboot.
