ksmbd: fix memory leak in smb2_lock()

In smb2_lock(), if setup_async_work() executes successfully,
work->cancel_argv will bind the argv that generated by kmalloc(). And
release_async_work() is called in ksmbd_conn_try_dequeue_request() or
smb2_lock() to release argv.
However, when setup_async_work function fails, work->cancel_argv has not
been bound to the argv, resulting in the previously allocated argv not
being released. Call kfree() to fix it.

Fixes: e2f34481

 ("cifsd: add server-side procedures for SMB3")
Signed-off-by: Zizhi Wo <wozizhi@huawei.com>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>