fix(owncloud): give redis a named data volume, as upstream does

owncloud/compose.yml

@@ -55,6 +55,8 @@ services:
     image: redis:6
     restart: unless-stopped
     command: ["--databases", "1"]
+    volumes:
+      - owncloud-redis-data:/data
     healthcheck:
       test: ["CMD", "redis-cli", "ping"]
       interval: 10s
@@ -64,3 +66,4 @@ services:
 volumes:
   owncloud-data:
   owncloud-mysql-data:
+  owncloud-redis-data: