usleep returns ESTOP when schedule timer failed

[chenBright]

What problem does this PR solve?

Issue Number:

Problem Summary:

_add_sleep_event失败后，bthread_usleep并没有真正sleep，只是重新调度了，这时候应该返回错误。一些场景下会有死循环风险，例如：

brpc/src/brpc/periodic_naming_service.cpp

Lines 64 to 71 in 13a0717

	if (bthread_usleep(GetNamingServiceAccessIntervalMs() * 1000UL) < 0) {
	if (errno == ESTOP) {
	RPC_VLOG << "Quit NamingServiceThread=" << bthread_self();
	return 0;
	}
	PLOG(FATAL) << "Fail to sleep";
	return -1;
	}

What is changed and the side effects?

Changed:

Side effects:

• Performance effects(性能影响):

• Breaking backward compatibility(向后兼容性):

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Check List:

• Please make sure your changes are compilable(请确保你的更改可以通过编译).
• When providing us with a new feature, it is best to add related tests(如果你向我们增加一个新的功能, 请添加相关测试).
• Please follow Contributor Covenant Code of Conduct.(请遵循贡献者准则).

[wwbmmm]

LGTM