Use listen instead of chained notifiers

From Ansible 2.2 onwards, listen can be used for
handlers instead of chaining notifiers. The
handlers are then executed in the sequence
present in the handler file.

Change-Id: I97a794220f3f97b41a70be5484ff48230214fa20

handlers/main.yml

@@ -13,13 +13,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-- name: Restart gnocchi services
-  command: "/bin/true"
-  notify:
-    - Stop services
-    - Copy new policy file into place
-    - Start services
-
 - name: Stop services
   service:
     name: "{{ item.value.service_name }}"
@@ -34,6 +27,7 @@
   until: _stop | success
   retries: 5
   delay: 2
+  listen: Restart gnocchi services
 
 # Note (odyssey4me):
 # The policy.json file is currently read continually by the services
@@ -51,6 +45,7 @@
     group: "{{ gnocchi_system_group_name }}"
     mode: "0640"
     remote_src: yes
+  listen: Restart gnocchi services
 
 - name: Start services
   service:
@@ -66,6 +61,7 @@
   until: _start | success
   retries: 5
   delay: 2
+  listen: Restart gnocchi services
 
 - name: Restart web server
   service: