Make the memcached dependency optional

Otherwise if you don't have memcached horizon will never
start.

Change-Id: Ibd3f5c5be20a70d6b7983b8ef9c0c34cd44a15cc

services/horizon/horizon.yml.j2

@@ -8,7 +8,11 @@ container:
 service:
   daemon:
     command: /usr/sbin/{{ apache_cmd }} -DFOREGROUND
-    dependencies: [horizon/bootstrap, memcached/daemon]
+    dependencies:
+      - horizon/bootstrap
+    {% if enable_memcached | bool %}
+      - memcached/daemon
+    {% endif %}
     files:
       000-default.conf:
         source: config/horizon/templates/horizon.conf.j2

tools/validate-service.py

@@ -91,6 +91,7 @@ def validate_command(filename, cmd, cmd_info, deps, role):
 
 def validate(filename, deps):
     mini_vars = {'cinder_volume_driver': 'lvm',
+                 'enable_memcached': 'yes',
                  'deployment_id': 'test'}
     role = filename.replace('.yml.j2', '')
     role_vars = ROLE_VARS_MAP.get(role, {})