tests: ensure that Ignition warnings are displayed on the console

Follow up to coreos#1621 (review)
This adds kola test coverage for displaying Ignition warnings
on the console.

tests/kola/ignition/warnings/config.ign

@@ -0,0 +1,14 @@
+{
+  "ignition": {
+    "version": "3.3.0"
+  },
+  "systemd": {
+    "units": [
+      {
+        "contents": "[Unit]\nDescription=echo service template\n[Service]\nType=oneshot\nExecStart=/bin/echo %i\n",
+        "enabled": true,
+        "name": "echo.service"
+      }
+    ]
+  }
+}

tests/kola/ignition/warnings/data/commonlib.sh

@@ -0,0 +1 @@
+../../../data/commonlib.sh

tests/kola/ignition/warnings/test.sh

@@ -0,0 +1,20 @@
+#!/bin/bash
+# kola: { "platforms": "qemu-unpriv" }
+# This test ensures that Ignition warnings 
+# are displayed on the console.
+
+set -xeuo pipefail
+
+. $KOLA_EXT_DATA/commonlib.sh
+
+warningsfile="/etc/issue.d/30_coreos_ignition_warnings.issue"
+
+# Make sure the motd file gets created 
+if ! test -f ${warningsfile}; then
+    fatal "not found ignition warnings issue file"
+fi
+# Checking for the warning
+if ! grep -e 'unit "echo.service" is enabled' ${warningsfile} ; then
+    fatal "failed to display Ignition warning on the console"
+fi
+ok "Successfully displayed Ignition warning on the console"