Zuul: add file extension to playbook path

Zuul now supports including the file extension on the playbook path
and omitting the extension is now deprecrated.  Update references
to include the extension.

Change-Id: I96ec4661aa1e14361f303649adb726fa52812645

.zuul.yaml

@@ -20,9 +20,9 @@
 
 - job:
     name: kolla-ansible-base
-    pre-run: tests/pre
-    run: tests/run
-    post-run: tests/post
+    pre-run: tests/pre.yml
+    run: tests/run.yml
+    post-run: tests/post.yml
     attempts: 1
     timeout: 10800
     required-projects:
@@ -34,7 +34,7 @@
 
 - job:
     name: kolla-ansible-centos-source
-    parent:  kolla-ansible-base
+    parent: kolla-ansible-base
     nodeset: kolla-ansible-centos
     voting: false
     vars:
@@ -61,7 +61,7 @@
 
 - job:
     name: kolla-ansible-centos-binary
-    parent:  kolla-ansible-base
+    parent: kolla-ansible-base
     nodeset: kolla-ansible-centos
     voting: false
     vars: