Add FIPS job

The job makes sure that functional tests pass when the nodes are
set to be in fips mode.

Depends-On: https://review.opendev.org/c/zuul/zuul-jobs/+/788778
Change-Id: Ib0388771ee1d9151850f4513f016b85b2970df93

playbooks/fips/enable-fips.yaml

@@ -0,0 +1,3 @@
+- hosts: all
+  roles:
+    - enable-fips

zuul.d/jobs.yaml

@@ -601,6 +601,14 @@
       bindep_profile: test py39
       python_version: 3.9
 
+- job:
+    name: openstack-tox-functional-py36-fips
+    parent: openstack-tox-functional-py36
+    nodeset: devstack-single-node-centos-8-stream
+    description: |
+      Functional testing for a FIPS enabled Centos 8 system
+    pre-run: playbooks/fips/enable-fips.yaml
+
 - job:
     name: openstack-tox-validate
     parent: openstack-tox