Revert "Solve Kombu filesystem transport not thread safe"

[karajan1001]

Reverts #1593
Sorry, the PR created by me works even worse than previous on our program. It only solved part of the problem and introduce a new one. I'll create a new PR later.

The previous problem comes from:

1. in _queue_bind

    def _queue_bind(self, exchange, routing_key, pattern, queue):
        queues = self.get_table(exchange)
        queue_val = exchange_queue_t(routing_key or "", pattern or "",
                                     queue or "")
        if queue_val not in queues:
            queues.insert(0, queue_val)
        with self._get_exchange_file_obj(exchange, "wb") as f_obj:
            f_obj.write(str_to_bytes(dumps(queues)))

We first read the table and then add a new line to it. We do add a lock during both progress but released it too quickly and the file might change between these two progress.
2. in _get and _purge we modified the data but didn't add a lock to them.

3. The new problem introduced by this PR.
   signal only works in the main thread.

Actually, I didn't expect it to be merged so quickly. Next time I'll add draft sign to any PR that hadn'd been carefully tested.

I'll create a new PR next Monday.

[lgtm-com]

This pull request introduces 1 alert when merging 0daad6c into 8699920 - view on LGTM.com

new alerts:

• 1 for Unused import

[auvipy]

better luck next time