test/kola: Test disabling units via Ignition

Test for: coreos/fedora-coreos-tracker#392

tests/kola/ignition/systemd-disable/config.bu

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+variant: fcos
+version: 1.4.0
+systemd:
+  units:
+    - name: zincati.service
+      enabled: false

tests/kola/ignition/systemd-disable/data/commonlib.sh

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+../../../data/commonlib.sh

tests/kola/ignition/systemd-disable/test.sh

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+#!/bin/bash
+# kola: { "distros": "fcos", "platforms": "qemu-unpriv" }
+# This test makes sure that ignition is able to disable units
+# https://github.com/coreos/fedora-coreos-tracker/issues/392
+
+# We don't need to test this on every platform. If it passes in
+# one place it will pass everywhere.
+# This test is currently scoped to FCOS because `zincati` is only available on
+# FCOS.
+# TODO-RHCOS: Determine if any services on RHCOS may be disabled and adapt test
+
+set -xeuo pipefail
+
+. $KOLA_EXT_DATA/commonlib.sh
+
+if [ "$(systemctl is-enabled zincati.service)" != 'disabled' ]; then
+    fatal "zincati.service systemd unit should be disabled"
+fi
+ok "zincati.service systemd unit is enabled"