Replace 20 lines of manual os.open/O_EXCL/fdopen/fsync/os.replace with the
existing atomic_json_write() from utils.py, which is already used by 6+
modules and handles temp-file creation, fsync, atomic replace, mode
control, and owner preservation. The only novel helper (_fsync_directory)
is retained — atomic_json_write does not do directory fsync.
Update test_flush_write_failure_leaves_no_recovery_file to monkeypatch
utils.os.replace (the new call path) instead of gateway.shutdown_flush.os.replace.
kshitij
720cdd1d14