CI: Ignore zuul.d

Zuul handles jobs updates just fine, no need to run k-a jobs
when touching zuul.d for different reasons.

Change-Id: I4e4dd1ff26ff46c47c84a9c144d9c91ae3e93a04

zuul.d/base.yaml

@@ -22,6 +22,7 @@
       - ^contrib/
       - ^specs/
       - ^kolla_ansible/tests/
+      - ^zuul\.d/
     vars:
       previous_release: train
       scenario: core