Add irrelevant-files to openstack-tox-functional*
Add irrelevant-files to openstack-tox-functional*

Adds these irrelevant files to openstack-tox-functional and
openstack-tox-functional-py35, since they don't affect the
functional tests:
  - ^.*\.rst$
  - ^doc/.*$
  - ^releasenotes/.*$

Change-Id: I56b4765bb4f350cc5a5e87e781614973bfcf9316

openstack-infra/openstack-zuul-jobs,openstack-infra/openstack-zuul-jobs