Cleanup irrelevant-files list in .zuul.yaml
Cleanup irrelevant-files list in .zuul.yaml

Periodic jobs ignore irrelevant-files, so remove this from periodic
jobs.

The list of irrelevant-files is the same everywhere, let's define it
only once - and then use it everywhere.

Change-Id: I8927de56a7e5f3354900fba10c2497035559a390

masayukig/tempest,openstack/tempest,openstack/tempest,cisco-openstack/tempest,masayukig/tempest,cisco-openstack/tempest