trivial: Add hacking checks to irrelevant-files in .zuul.yaml

This is to skip over hacking modifications triggering all Patrole
Zuul jobs as in [0]. Besides, Tempest also skips hacking in its
irrelevant-files [1]. Also do this for etc/.

[0] https://review.openstack.org/#/c/614655/3
[1] https://github.com/openstack/tempest/blob/da8aec9aedcac940ba1dbc3beee50f05f13af3f1/.zuul.yaml#L326

Change-Id: Iee5b634e77c2faaa36d3d19a3b56b1fec685aa7e
1 file changed