test: Use a non distro-specific method to mark an interface as unmanaged by NM
test: Use a non distro-specific method to mark an interface as unmanaged by NM

Fedora CoreOS does not support the old sysconfig scripts any more.
Current Ubuntu has also dropped ifupdown long ago, just NM parses that
still.

martinpitt/cockpit,mvollmer/cockpit,deryni/cockpit,cockpit-project/cockpit,cockpituous/cockpit,cockpit-project/cockpit,deryni/cockpit,martinpitt/cockpit,cockpit-project/cockpit,moraleslazaro/cockpit,cockpituous/cockpit,cockpituous/cockpit,cockpituous/cockpit,moraleslazaro/cockpit,garrett/cockpit,mvollmer/cockpit,mvollmer/cockpit,cockpituous/cockpit,deryni/cockpit,mvollmer/cockpit,martinpitt/cockpit,deryni/cockpit,deryni/cockpit,garrett/cockpit,moraleslazaro/cockpit,cockpituous/cockpit,cockpit-project/cockpit,martinpitt/cockpit,moraleslazaro/cockpit,cockpit-project/cockpit,deryni/cockpit,moraleslazaro/cockpit,deryni/cockpit,garrett/cockpit,martinpitt/cockpit,mvollmer/cockpit,moraleslazaro/cockpit,moraleslazaro/cockpit,garrett/cockpit,garrett/cockpit