nixos/redis: enforce owner/perms on /var/lib/redis (#18046)

Previously it was only set once, now it is enforced on each start-up of
redis.service. Also set _ownership_ recursively, so that the
/var/lib/redis/dump.rdb file is guaranteed to be accessible by the
currently configured redis user.

Fixes issue #9687, where redis wouldn't start because /var/lib/redis had
wrong owner.

nixos/modules/services/databases/redis.nix

@@ -234,9 +234,8 @@ in
         serviceConfig.Type = "oneshot";
 
         script = ''
-          if ! test -e ${cfg.dbpath}; then
-              install -d -m0700 -o ${cfg.user} ${cfg.dbpath}
-          fi
+          install -d -m0700 -o ${cfg.user} ${cfg.dbpath}
+          chown -R ${cfg.user} ${cfg.dbpath}
         '';
       };