Test driver-requirements changes on standalone job

This job installs ansible from the driver-requirements.txt file, but we
aren't running the job on changes to this file. Override
irrelevant-files for this job to ensure updates to the ansible
dependency are tested.

Change-Id: I7fca8123ecffe24087db25aff4cd9c41560cf2be

zuul.d/legacy-ironic-jobs.yaml

@@ -107,6 +107,18 @@
     parent: legacy-ironic-dsvm-base
     run: playbooks/legacy/ironic-dsvm-standalone/run.yaml
     timeout: 10800
+    irrelevant-files:
+      - ^test-requirements.txt$
+      - ^.*\.rst$
+      - ^api-ref/.*$
+      - ^doc/.*$
+      - ^install-guide/.*$
+      - ^ironic/locale/.*$
+      - ^ironic/tests/.*$
+      - ^releasenotes/.*$
+      - ^setup.cfg$
+      - ^tools/.*$
+      - ^tox.ini$
     required-projects:
       - openstack-infra/devstack-gate
       - openstack/ironic