Local storage retains its thread lock after IPC acquisition fails #2202

Summary

LockLocalStorage.__enter__() leaves its thread lock acquired if the IPC lock times out or raises an exception. Since a failed __enter__ does not call __exit__, reusing the same lock object cannot acquire the thread lock again, even after the IPC contention is gone.

Detailed Information

Reproduced on current trunk (bd9cbb3e393bc42f57684481e7c62e9293007584), Python 3.12/macOS. This deterministic reproducer models the documented false return from fasteners.InterProcessLock.acquire() when its timeout expires:

import os
import tempfile
from unittest.mock import patch
from libcloud.storage.drivers.local import LockLocalStorage
from libcloud.common.types import LibcloudError

with tempfile.TemporaryDirectory() as root:
    lock = LockLocalStorage(os.path.join(root, "object"))
    with patch.object(lock.ipc_lock, "acquire", return_value=False):
        try:
            lock.__enter__()
        except LibcloudError:
            pass
    print(lock.thread_lock.locked())  # True

The thread lock should be released before propagating acquisition failure. The same leak occurs if IPC acquisition raises OSError or is interrupted by KeyboardInterrupt.

This is separate from #1975 / #2172, which address leftover lock files after a successful acquisition.