Add Zuul v3 native unit-tests

Add new job to replace legacy-devstack-unit-tests.

Conflicts:
        .zuul.yaml

Change-Id: I4fe59b1954514a7146a4412e3103a0a05a9250f2
(cherry picked from commit 838b833b63)

.zuul.yaml

@@ -315,6 +315,15 @@
       - playbooks/tox/pre.yaml
     run: playbooks/tox/run.yaml
 
+- job:
+    name: devstack-unit-tests
+    description: |
+      Runs unit tests on devstack project.
+
+      It runs  ``run_tests.sh``.
+    pre-run: playbooks/unit-tests/pre.yaml
+    run: playbooks/unit-tests/run.yaml
+
 - project:
     templates:
       - integrated-gate
@@ -324,6 +333,7 @@
       jobs:
         - devstack
         - devstack-multinode
+        - devstack-unit-tests
         - openstack-tox-bashate
         - ironic-tempest-dsvm-ipa-wholedisk-bios-agent_ipmitool-tinyipa:
             voting: false
@@ -352,6 +362,7 @@
     gate:
       jobs:
         - devstack
+        - devstack-unit-tests
         - openstack-tox-bashate
         - neutron-grenade-multinode:
             irrelevant-files:

playbooks/unit-tests/pre.yaml

@@ -0,0 +1,13 @@
+- hosts: all
+
+  tasks:
+
+    - name: Install prerequisites
+      shell:
+        chdir: '{{ zuul.project.src_dir }}'
+        executable: /bin/bash
+        cmd: |
+          set -e
+          set -x
+          echo "IPV4_ADDRS_SAFE_TO_USE=10.1.0.0/20" >> localrc
+          ./tools/install_prereqs.sh

playbooks/unit-tests/run.yaml

@@ -0,0 +1,12 @@
+- hosts: all
+
+  tasks:
+
+    - name: Run run_tests.sh
+      shell:
+        chdir: '{{ zuul.project.src_dir }}'
+        executable: /bin/bash
+        cmd: |
+          set -e
+          set -x
+          ./run_tests.sh