Test for invalid scroll_size

modules/reindex/src/test/resources/rest-api-spec/test/update_by_query/20_validation.yaml

@@ -26,6 +26,20 @@
         index: test
         size: -4
 
+---
+"invalid scroll_size fails":
+  - do:
+      index:
+        index:   test
+        type:    test
+        id:      1
+        body:    { "text": "test" }
+  - do:
+      catch: /Failed to parse int parameter [scroll_size] with value [asdf]/
+      update_by_query:
+        index: test
+        scroll_size: asdf
+
 ---
 "requests_per_second cannot be an empty string":
   - do: