Do not fail on stackviz issues

The process-stackviz role only helps with analyzing runs, when it fails
it should not cause the whole job to suffer a POST_FAILURE.

Change-Id: Icfd6b2fc7adb42afb7900ea4458fa60cefc76fdb
Related-Bug: 1758054
diff --git a/roles/process-stackviz/tasks/main.yaml b/roles/process-stackviz/tasks/main.yaml
index 82f8f3d..3724e0e 100644
--- a/roles/process-stackviz/tasks/main.yaml
+++ b/roles/process-stackviz/tasks/main.yaml
@@ -50,6 +50,7 @@
     - stackviz_archive.stat.exists
     - subunit_input.stat.exists
     - dstat_input.stat.exists
+  failed_when: False
 
 - name: Run stackviz without dstat
   shell: |
@@ -61,3 +62,4 @@
     - stackviz_archive.stat.exists
     - subunit_input.stat.exists
     - not dstat_input.stat.exists
+  failed_when: False