Use fetch-subunit-output role

Currently there is a zuul-jobs role only used in this tempest job while
other jobs mostly use fetch-subunit-output role.

This changes tries to consolidate towards the most used role, to be able
to clean up zuul-jobs a bit.

Change-Id: I404760ba34767660f8816f48712e13dccad67440
Depends-On: https://review.openstack.org/548406
diff --git a/roles/process-stackviz/defaults/main.yaml b/roles/process-stackviz/defaults/main.yaml
index c6a64d1..f3bc32b 100644
--- a/roles/process-stackviz/defaults/main.yaml
+++ b/roles/process-stackviz/defaults/main.yaml
@@ -1,3 +1,3 @@
 devstack_base_dir: /opt/stack
 stage_dir: "{{ ansible_user_dir }}"
-test_results_stage_name: test_results
+zuul_work_dir: "{{ devstack_base_dir }}/tempest"