Move check logic into #batch_operation_disallowed?

app/controllers/projects/lfs_api_controller.rb

@@ -98,7 +98,7 @@ class Projects::LfsApiController < Projects::GitHttpClientController
   end
 
   def lfs_check_batch_operation!
-    if upload_request? && Gitlab::Database.read_only?
+    if batch_operation_disallowed?
       render(
         json: {
           message: lfs_read_only_message
@@ -109,6 +109,11 @@ class Projects::LfsApiController < Projects::GitHttpClientController
     end
   end
 
+  # Overridden in EE
+  def batch_operation_disallowed?
+    upload_request? && Gitlab::Database.read_only?
+  end
+
   # Overridden in EE
   def lfs_read_only_message
     _('You cannot write to this read-only GitLab instance.')