Performance Issues

## Summary
I have some months using Libcloud v2.3.0, now when I tried to update to v2.5.0 with the same application files I'm getting a lot of errors.

## Detailed Information
Using the same server and applications **with v2.5.0 scripts stop responding and freezing very often** (like 10%) and randomly (can't reproduce it), it never happens with v2.3.0. I'm just using some simple scripts for Digital Ocean and AWS to create, stop and terminate servers, and also listing some things like images, locations, sizes and keys.

Python 3.6.8
Ubuntu 18.04

Now I've downgraded again to v2.3.0 and everything is normal and stable as usual.

For more information on contributing, please see https://libcloud.readthedocs.io/en/latest/development.html

首先，针对所述的 AWS 和 DigitalOcean 操作，对比 Ubuntu 18.04 上使用 Python 3.6.8 的应用脚本与 Libcloud v2.3.0 和 v2.5.0。记录日志或回溯信息，并将间歇性冻结范围缩小到一个可复现的回归问题；完成的标准是脚本在较新版本上仍保持响应和稳定。

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