restapi: prefer parentType over subclasses in getParent

Currently LinkHelper#getParent may return subclasses even if the
parentType exists in the methods list.

This makes the returned resource unpredicatble as the method list does
not have any guaranteed order.

To fix this, this patch tries to match parentType first, and only if it
is not in the list it will fallback to a subclass.

Bug-Url: https://bugzilla.redhat.com/2080728
Signed-off-by: Benny Zlotnik <bzlotnik@redhat.com>

backend/manager/modules/restapi/jaxrs/src/main/java/org/ovirt/engine/api/restapi/util/LinkHelper.java

@@ -225,18 +225,26 @@ private static void unsetInlineResource(BaseResource model, Class<?> type) {
      * @return           the parent object, or null if not set
      */
     private static <R extends BaseResource> BaseResource getParent(R model, Class<?> parentType) {
+        Object assignedFromParent = null;
+
+        // Try to match a method whose parent matches parentType first, only fallback to a subclass if parentType was
+        // not found in the list.
         for (Method method : getRelevantMethods(model.getClass())) {
             try {
                 Object potentialParent = method.invoke(model);
+                if (potentialParent != null && potentialParent.getClass().equals(parentType)) {
+                    return (BaseResource) potentialParent;
+                }
                 if (potentialParent != null && parentType.isAssignableFrom(potentialParent.getClass())) {
-                    return (BaseResource)potentialParent;
+                    assignedFromParent = potentialParent;
                 }
             } catch (Exception e) {
                 log.error("Error invoking method when adding links to an API entity", e);
                 continue;
             }
         }
-        return null;
+
+        return (BaseResource) assignedFromParent;
     }
 
     /**