[train,ussuri] Set cinder's __DEFAULT__ vol type description

Update the description of cinder's internal __DEFAULT__ volume type
so that users don't confuse it with the actual default volume type
established by the CinderDefaultVolumeType parameter.

This patch is a variant of Idf27c14b31dc077ef9a0e567bd502ed6842bd52b,
which in later releases deletes cinder's __DEFAULT__ volume type if
there are no volumes associated with it. However, the __DEFAULT__
volume type cannot be removed prior to the victoria release because
it's required for a DB migration.

Lastly, CinderDefaultVolumeType is now constrained to prevent it being
set to an empty string. That should never happen, so this is just a
safety net.

Change-Id: Ifc35eb09ab3af4d8f3ea232dd20558047c6834b9
Related-Bug: #1782217
(cherry picked from commit d30105a28c)

deployment/cinder/cinder-api-container-puppet.yaml

@@ -58,6 +58,11 @@ parameters:
     default: tripleo
     description: The name of Cinder's default volume type.
     type: string
+    constraints:
+    - allowed_pattern: "[a-zA-Z0-9]+"
+      description: >
+        The default volume type must be at least 1 character and contain only
+        letters and numbers.
   CinderEnableDBPurge:
     default: true
     description: |
@@ -497,7 +502,7 @@ outputs:
             state: absent
           when:
             - step|int == 4
-        - name: Manage Cinder Volume Type
+        - name: Manage Cinder's default volume type
           become: true
           vars:
             default_volume_type: {get_param: CinderDefaultVolumeType}
@@ -510,6 +515,13 @@ outputs:
             if ! openstack volume type show "{{ default_volume_type }}"; then
                 openstack volume type create --public "{{ default_volume_type }}"
             fi
+            eval $(openstack volume type show __DEFAULT__ -f shell -c id -c description)
+            if [ -n "$id" ]; then
+                tripleo_descr="For internal use, '{{ default_volume_type }}' is the default volume type"
+                if [ "$description" != "$tripleo_descr" ]; then
+                    openstack volume type set $id --description "$tripleo_descr"
+                fi
+            fi
           args:
             executable: /bin/bash
           changed_when: false

releasenotes/notes/cinder-update-volume-type-description-5f81e2ff5ea8184a.yaml

@@ -0,0 +1,6 @@
+---
+other:
+  - |
+    The description of cinder's own __DEFAULT__ volume type is updated to
+    indicate the actual default volume type is the one established by the
+    CinderDefaultVolumeType parameter.