build_wrapper: Fix some warnings reported by pylint

  C:1097,16:handle_installer_build: Comma not followed by a space
                save_latest_successful_installer(offline_installer_build,installer_name, installer_name_final, latest_successful_dir, installer_output_dir)
                                                                        ^^
  C:1118,16:handle_installer_build: Comma not followed by a space
                save_latest_successful_installer(offline_installer_build,installer_name, installer_name_final, latest_successful_dir, installer_output_dir)
                                                                        ^^
  C:1136,16:handle_installer_build: Comma not followed by a space
                save_latest_successful_installer(offline_installer_build,installer_name, installer_name_final, latest_successful_dir, installer_output_dir)

Change-Id: Ia5b98a81e42c36e3e6944451ddde493dc22aa277
Reviewed-by: Iikka Eklund <iikka.eklund@digia.com>