nvmet-auth: Synchronize timeout work during SQ teardown

In the Linux kernel, the following vulnerability has been resolved: nvmet-auth: Synchronize timeout work during SQ teardown nvmet_auth_sq_free() cancels auth_expired_work with cancel_delayed_work(). If the work has already started, cancellation does not wait for the callback. Transport teardown can consequently free or reuse the queue containing struct nvmet_sq while nvmet_auth_expired_work() still accesses that SQ. Add a teardown-specific helper that synchronously drains the delayed work before freeing authentication state, and use it from nvmet_sq_destroy(). Keep the non-synchronous helper for in-band authentication state cleanup, where the SQ owner remains alive.