Switch to consolidated fetch-subunit-output role

fetch-testr-output and fetch-stestr-output are being merged.

Change-Id: I00d448c4e6b98a1f504b048c74eff4e110c0b511
Depends-On: I833320cf9a932d8e119645eb798ce0c93d854321
diff --git a/playbooks/tox/post.yaml b/playbooks/tox/post.yaml
index d9e299f..7f0cb19 100644
--- a/playbooks/tox/post.yaml
+++ b/playbooks/tox/post.yaml
@@ -1,5 +1,4 @@
 - hosts: all
   roles:
     - fetch-tox-output
-    - fetch-testr-output
-    - fetch-stestr-output
+    - fetch-subunit-output