Add heat parameter for all of config_volume images

This commit consistently defines a heat template parameter in the form
of DockerXXXConfigImage where XXX represents the name of the
config_volume that is used by docker-puppet.

The goal is to mitigate hard to debug errors where the templates would
set different defaults for the image docker-puppet.py uses to run, for
the same config_volume name.

This fixes a couple of inconsistencies on the way.

Change-Id: I212020a76622a03521385a6cae4ce73e51ce5b6b
Closes-Bug: #1699791

docker/services/gnocchi-metricd.yaml

@@ -12,6 +12,10 @@ parameters:
     description: image
     default: 'centos-binary-gnocchi-metricd:latest'
     type: string
+  DockerGnocchiConfigImage:
+    description: The container image to use for the gnocchi config_volume
+    default: 'centos-binary-gnocchi-api:latest'
+    type: string
   EndpointMap:
     default: {}
     description: Mapping of service endpoint -> protocol. Typically set
@@ -63,10 +67,10 @@ outputs:
         config_volume: gnocchi
         puppet_tags: gnocchi_config
         step_config: *step_config
-        config_image: &gnocchi_metricd_image
+        config_image:
           list_join:
             - '/'
-            - [ {get_param: DockerNamespace}, {get_param: DockerGnocchiMetricdImage} ]
+            - [ {get_param: DockerNamespace}, {get_param: DockerGnocchiConfigImage} ]
       kolla_config:
         /var/lib/kolla/config_files/gnocchi_metricd.json:
           command: /usr/bin/gnocchi-metricd
@@ -77,7 +81,10 @@ outputs:
       docker_config:
         step_4:
           gnocchi_metricd:
-            image: *gnocchi_metricd_image
+            image:
+              list_join:
+                - '/'
+                - [ {get_param: DockerNamespace}, {get_param: DockerGnocchiMetricdImage} ]
             net: host
             privileged: false
             restart: always