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: I4bff5f12742364f7cc92e17869a047fd2185dda4
diff --git a/.zuul.yaml b/.zuul.yaml
index 389ada5..710b229 100644
--- a/.zuul.yaml
+++ b/.zuul.yaml
@@ -48,7 +48,7 @@
         ADMIN_PASSWORD: secretadmin
         SERVICE_PASSWORD: secretservice
         NETWORK_GATEWAY: 10.1.0.1
-        Q_USE_DEBUG_COMMAND: True
+        Q_USE_DEBUG_COMMAND: true
         FIXED_RANGE: 10.1.0.0/20
         IPV4_ADDRS_SAFE_TO_USE: 10.1.0.0/20
         FLOATING_RANGE: 172.24.5.0/24
@@ -56,25 +56,24 @@
         FLOATING_HOST_PREFIX: 172.24.4
         FLOATING_HOST_MASK: 23
         SWIFT_REPLICAS: 1
-        SWIFT_START_ALL_SERVICES: False
+        SWIFT_START_ALL_SERVICES: false
         LOGFILE: /opt/stack/logs/devstacklog.txt
-        LOG_COLOR: False
-        VERBOSE: True
-        NETWORK_GATEWAY: 10.1.0.1
-        NOVNC_FROM_PACKAGE: True
-        ERROR_ON_CLONE: True
+        LOG_COLOR: false
+        VERBOSE: true
+        NOVNC_FROM_PACKAGE: true
+        ERROR_ON_CLONE: true
         # Gate jobs can't deal with nested virt. Disable it.
         LIBVIRT_TYPE: qemu
         # NOTE(dims): etcd 3.x is not available in debian/ubuntu
         # etc. As a stop gap measure, devstack uses wget to download
         # from the location below for all the CI jobs.
-        ETCD_DOWNLOAD_URL: "http://tarballs.openstack.org/etcd/"
+        ETCD_DOWNLOAD_URL: http://tarballs.openstack.org/etcd/
       devstack_services:
-        horizon: False
-        tempest: False
-    pre-run: playbooks/pre
-    run: playbooks/devstack
-    post-run: playbooks/post
+        horizon: false
+        tempest: false
+    pre-run: playbooks/pre.yaml
+    run: playbooks/devstack.yaml
+    post-run: playbooks/post.yaml
 
 
 - project: