Fix functional tests job

This patch fixes functional tests job by doing 2 things:

* Configure correct db user in the functional tests job
  This was changed in the Neutron in commit [1] and should
  be updated also in the configure_functional_tests role in
  this repo.
* Remove run-devstack role from run_functional_job playbook
  There is no need to run that role in the functional
  job and not running it can save few minutes in each job's run.
  The same change was done in Neutron in patch [2].

[1] https://review.opendev.org/c/openstack/neutron/+/814009
[2] https://review.opendev.org/c/openstack/neutron/+/816354

Depends-On: https://review.opendev.org/c/openstack/devstack/+/819402

Closes-bug: #1952357
Change-Id: I0f3f93cdb361575591cd1278da74075d83611cae

playbooks/run_functional_job.yaml

@@ -1,7 +1,5 @@
 - hosts: all
   roles:
-    - run-devstack
-    # Run bindep and test-setup after devstack so that they won't interfere
     - role: bindep
       bindep_profile: test
       bindep_dir: "{{ zuul_work_dir }}"

roles/configure_functional_tests/tasks/main.yaml

@@ -15,6 +15,8 @@
         STACK_USER=stack
         OVS_BRANCH={{ OVS_BRANCH }}
         OVN_BRANCH={{ OVN_BRANCH }}
+        # This is DB USER used in e.g. pgsql db
+        DATABASE_USER=openstack_citest
 
         source $DEVSTACK_PATH/functions
         source $DEVSTACK_PATH/lib/neutron_plugins/ovs_source