Run tempest with its defaults

By default, tempest runs in parallel, with the amount of workers
depending on the CPU.

This adds an optional variable to define the concurrency or
serialization.

Change-Id: I7054cf78bbac9f84095d4b66d00f9d2cfea25ac5

defaults/main.yml

@@ -23,6 +23,8 @@ tempest_pip_package_state: "latest"
 
 # Toggle whether tempest actually executes
 tempest_run: no
+# Define 0 (serial) or more to use a non default concurrency
+#tempest_run_concurrency:
 
 tempest_git_repo: https://git.openstack.org/openstack/tempest
 tempest_git_install_branch: master

tasks/tempest_run.yml

@@ -17,7 +17,7 @@
   - name: Execute tempest tests
     shell: |
       . {{ tempest_venv_bin }}/activate
-      tempest run --serial --whitelist-file {{ tempest_test_whitelist_file_path }}
+      tempest run {% if tempest_run_concurrency is defined %}{% if tempest_run_concurrency | int > 0 %}--concurrency {{ tempest_run_concurrency | int }}{% else %}--serial{% endif %}{% endif %} --whitelist-file {{ tempest_test_whitelist_file_path }}
     args:
       chdir: "{{ tempest_venv_bin | dirname }}/workspace"
       executable: /bin/bash