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/README.rst b/roles/process-stackviz/README.rst
index 54c217b..a8447d2 100644
--- a/roles/process-stackviz/README.rst
+++ b/roles/process-stackviz/README.rst
@@ -16,7 +16,7 @@
    The stage directory where the input data can be found and
    the output will be produced.
 
-.. zuul:rolevar:: test_results_stage_name
-   :default: test_results
+.. zuul:rolevar:: zuul_work_dir
+   :default: {{ devstack_base_dir }}/tempest
 
-   The name of the subunit file to be used as input.
+   Directory to work in. It has to be a fully qualified path.