server: fix additional zones cannot be removed (#9261)

Got an exception when delete a zone

```
com.cloud.utils.exception.CloudRuntimeException: The zone cannot be deleted because there are Secondary storages in this zone
```

Author: weizhouapache

engine/schema/src/main/java/org/apache/cloudstack/storage/datastore/db/ImageStoreDaoImpl.java

@@ -130,7 +130,7 @@ public List<ImageStoreVO> findByZone(ZoneScope scope, Boolean readonly) {
         }
         if (scope.getScopeId() != null) {
             SearchCriteria<ImageStoreVO> scc = createSearchCriteria();
-            scc.addOr("scope", SearchCriteria.Op.EQ, ScopeType.ZONE);
+            scc.addOr("scope", SearchCriteria.Op.EQ, ScopeType.REGION);
             scc.addOr("dcId", SearchCriteria.Op.EQ, scope.getScopeId());
             sc.addAnd("scope", SearchCriteria.Op.SC, scc);
         }