test: Use veth instead of assuming an eth1 in TestNetworking.testNoService
test: Use veth instead of assuming an eth1 in TestNetworking.testNoService

eth1 is a specific feature of our cockpit VMs, and does not exist in
e. g. the Fedora gating test VMs. Use a veth instead, so that in the
future we can make this test nondestructive and run it downstream.

Closes #13788

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