Switch legacy-tempest-neutron-full-stable to focal

legacy-tempest-neutron-full-stable deploy's stable/wallaby
and is running on ubuntu-bionic(py3.6) and failing in tempest
setup as tempest master no longer works with py3.6.

Master is dropping py3.6 support, currently oslo.log has already
dropped the support and it's latest release is not installable
on py3.6.

Pin Markusafe, as since version 2.1.0 it dropped
module 'soft_unicode' which is required by Jinja2.

Also update ansible version to 2.9.6 as of focal
which should auto discover python as per distro.

So let's switch this job to ubuntu-focal which is py3.8.

Change-Id: I37887bf430b4bce2b9d2179b2d6dd6c050bb1768

.zuul.yaml

@@ -4,6 +4,12 @@
       - name: primary
         label: ubuntu-xenial
 
+- nodeset:
+    name: legacy-ubuntu-focal
+    nodes:
+      - name: primary
+        label: ubuntu-focal
+
 - job:
     name: devstack-gate-hooks
     parent: legacy-dsvm-base
@@ -17,6 +23,7 @@
     run: playbooks/legacy/tempest-neutron-full/run.yaml
     post-run: playbooks/legacy/tempest-neutron-full/post.yaml
     timeout: 10800
+    nodeset: legacy-ubuntu-focal
     required-projects:
       - openstack/devstack-gate
       - openstack/neutron

devstack-vm-gate-wrap.sh

@@ -28,9 +28,9 @@ GIT_BRANCH=${GIT_BRANCH:-master}
 # We're using enough ansible specific features that it's extremely
 # possible that new ansible releases can break us. As such we should
 # be very deliberate about which ansible we use.
-# NOTE(mriedem): Ansible 2.7.14 is current as of Ubuntu Xenial 16.04.
+# NOTE(ykarel): Ansible 2.9.6 is current as of Ubuntu Focal 20.04.
 # ARA is pinned to <1.0.0 below which affects the required version of Ansible.
-ANSIBLE_VERSION=${ANSIBLE_VERSION:-2.7.14}
+ANSIBLE_VERSION=${ANSIBLE_VERSION:-2.9.6}
 export DSTOOLS_VERSION=${DSTOOLS_VERSION:-0.4.0}
 
 # Set to 0 to skip stackviz
@@ -528,7 +528,8 @@ virtualenv -p python${PYTHON_VER} /tmp/ansible
 /tmp/ansible/bin/pip install pbr
 /tmp/ansible/bin/pip install ansible==$ANSIBLE_VERSION \
                 devstack-tools==$DSTOOLS_VERSION 'ara<1.0.0' 'cmd2<0.9.0' \
-                'flask<2.0.0' 'alembic<1.5.0' 'importlib-resources<5.1.3'
+                'flask<2.0.0' 'alembic<1.5.0' 'importlib-resources<5.1.3' \
+                'MarkupSafe<2.1.0'
 export ANSIBLE=/tmp/ansible/bin/ansible
 export ANSIBLE_PLAYBOOK=/tmp/ansible/bin/ansible-playbook
 export ANSIBLE_CONFIG="$WORKSPACE/ansible.cfg"