Cinder containers: volume and env customizations

This patch will allow custom volume and env variables for the
cinder-volume container.

This is likely going to be needed by some Cinder backends who may not
have in-tree TripleO integration yet and need these types of
customizations.

Change-Id: I825c5373c7c4ab6896579eae705bc034f67fb68f

docker/services/cinder-volume.yaml

@@ -52,6 +52,14 @@ parameters:
   CephClientUserName:
     default: openstack
     type: string
+  CinderVolumeOptVolumes:
+    default: []
+    description: list of optional volumes to be mounted
+    type: comma_delimited_list
+  CinderVolumeOptEnvVars:
+    default: []
+    description: list of optional environment variables
+    type: comma_delimited_list
 
 resources:
 
@@ -143,6 +151,7 @@ outputs:
             volumes:
               list_concat:
                 - {get_attr: [ContainersCommon, volumes]}
+                - {get_param: CinderVolumeOptVolumes}
                 -
                   - /var/lib/kolla/config_files/cinder_volume.json:/var/lib/kolla/config_files/config.json:ro
                   - /var/lib/config-data/puppet-generated/cinder/:/var/lib/kolla/config_files/src:ro
@@ -155,7 +164,10 @@ outputs:
                   - /var/lib/cinder:/var/lib/cinder
                   - /var/log/containers/cinder:/var/log/cinder
             environment:
-              - KOLLA_CONFIG_STRATEGY=COPY_ALWAYS
+              list_concat:
+                - {get_param: CinderVolumeOptEnvVars}
+                -
+                  - KOLLA_CONFIG_STRATEGY=COPY_ALWAYS
       host_prep_tasks:
         - name: create persistent directories
           file: