tests/misc-ro: generalize NIC naming test

Instead of checking for `ens` on QEMU, just check that the interface
name *isn't* `eth*`. This should be cross-platform, so we can drop the
`systemd-run` wrapper.

tests/kola/misc-ro

@@ -1,6 +1,6 @@
 #!/bin/bash
 # This is a place to put random quick read-only tests.
-set -euo pipefail
+set -xeuo pipefail
 
 ok() {
     echo "ok" "$@"
@@ -15,5 +15,7 @@ systemctl is-enabled logrotate.service
 ok logrotate
 
 # https://github.com/coreos/fedora-coreos-config/commit/2a5c2abc796ac645d705700bf445b50d4cda8f5f
-systemd-run -P -p ConditionVirtualization=kvm --wait /bin/sh -c 'set -euo pipefail; ip link | grep -o -e " ens[0-9]:"'
+if ip link | grep -o -e " eth[0-9]:"; then
+    fatal "detected eth* NIC naming on node"
+fi
 ok nic naming