fix FileSystemOperator.write_a_file. ignore path only after affermative server response.
add test setexecuter for ServerCommunicator
add test get_url_relpath for ServerCommunicator
add add_event_to_ignore test for FileSystemOperator
add case in test to improve coverage
remove refuse mock method
add CommandExecuter test
add DirSnapshotManager.syncronize_dispatcher test