Pass tox_extra_args to Run tempest task

Patrole needs access to global packages, but the 'all-plugin' is
deprecated[0] and 'all' defines a sitepackages option as False[1].
Adding tox_extra_args option makes it possible to configure Zuul and
pass --sitepackages argument to tox.

[0] https://github.com/openstack/tempest/blob/9b4c50cf634cbea6e6a7353fff14c2f0a7ab1aa2/tox.ini#L64
[1] https://github.com/openstack/tempest/blob/9b4c50cf634cbea6e6a7353fff14c2f0a7ab1aa2/tox.ini#L7

Change-Id: Ib3264f54075216471720483c8dd816887c1f413c
diff --git a/roles/run-tempest/tasks/main.yaml b/roles/run-tempest/tasks/main.yaml
index 54ddc71..16086aa 100644
--- a/roles/run-tempest/tasks/main.yaml
+++ b/roles/run-tempest/tasks/main.yaml
@@ -35,7 +35,7 @@
       when: blacklist_stat.stat.exists
 
 - name: Run Tempest
-  command: tox -e {{tox_envlist}} -- {{tempest_test_regex|quote}} {{blacklist_option|default('')}} \
+  command: tox -e {{tox_envlist}} {{tox_extra_args}} -- {{tempest_test_regex|quote}} {{blacklist_option|default('')}} \
             --concurrency={{tempest_concurrency|default(default_concurrency)}} \
             --black-regex={{tempest_black_regex|quote}}
   args: