Add role to build the stackviz report

Add a role to build the stackviz report and include it in the
tempest post play.

Change-Id: I085460fc7a4fe6baee2d85c8ab3ea3a2128ea54d
diff --git a/roles/process-stackviz/README.rst b/roles/process-stackviz/README.rst
new file mode 100644
index 0000000..b05326d
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+Generate stackviz report.
+
+Generate stackviz report using subunit and dstat data, using
+the stackviz archive embedded in test images.
+
+**Role Variables**
+
+.. zuul:rolevar:: devstack_base_dir
+   :default: /opt/stack
+
+   The devstack base directory.
+
+.. zuul:rolevar:: stage_dir
+   :default: /opt/stack/logs
+
+   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
+
+   The name of the subunit file to be used as input.