tests,json: Fix match if the first child differs

* tests/json/t-json.c (test_contains): Try all siblings of
the haystack child.

--
This fixes the case where we don't match against the
first child because the order might have changed or
a new element was inserted at the top. Then we
have to try out also all the siblings.

tests/json/t-json.c

@@ -153,10 +153,22 @@ test_contains (cjson_t needle, cjson_t hay)
                    nonnull (needle->string));
         }
       if (test_contains (needle->child, hay->child))
+        {
+          int found = 0;
+          for (cjson_t hit = hay->child; hit; hit = hit->next)
+            {
+              found |= !test_contains (needle->child, hit);
+              if (found)
+                {
+                  break;
+                }
+            }
+          if (!found)
             {
               return 1;
             }
         }
+    }
 
   if (needle->prev)
     {