Folder reload runs twice

Issue discovered in the process of diagnosing #918:

thunar_folder_reload always runs twice. First it's called with reload_info=true. At the bottom of thunar_folder_finished there is a call to thunar_file_reload (folder->corresponding_file), which sends a signal hooked up to thunar_folder_file_changed which calls thunar_folder_reload again. This time with reload_info=false, so there is no endless loop.