Support Redis cluster in Redis data-source extension

[TinChi0818]

Issue Description

在Redis单机模式下，sentinel可以工作。在Redis集群模式下，报错host is empty。
文档中仅有单机、哨兵模式如何构建：

Describe what happened (or what feature you want)

Describe what you expected to happen

How to reproduce it (as minimally and precisely as possible)

Tell us your environment

jdk1.8

Anything else we need to know?

[sczyh30]

Hi, Redis cluster is not supported yet in Redis data-source. Contributions are welcomed!

[liqiangz]

I will solve this issue.

[TinChi0818]

thanks------------------&nbsp;原始邮件&nbsp;------------------ 发件人:&nbsp;&quot;liqiangz&quot;<notifications@github.com&gt; 发送时间:&nbsp;2020年9月19日(星期六) 晚上7:24 收件人:&nbsp;&quot;alibaba/Sentinel&quot;<Sentinel@noreply.github.com&gt;; 抄送:&nbsp;&quot;TinChi0818&quot;<798130689@qq.com&gt;;&quot;Author&quot;<author@noreply.github.com&gt;; 主题:&nbsp;Re: [alibaba/Sentinel] Support Redis cluster in Redis data-source extension (#1749)

[TinChi0818]

ok------------------&nbsp;原始邮件&nbsp;------------------ 发件人:&nbsp;&quot;Eric&amp;nbsp;Zhao&quot;<notifications@github.com&gt; 发送时间:&nbsp;2020年9月18日(星期五) 晚上7:34 收件人:&nbsp;&quot;alibaba/Sentinel&quot;<Sentinel@noreply.github.com&gt;; 抄送:&nbsp;&quot;TinChi0818&quot;<798130689@qq.com&gt;;&quot;Author&quot;<author@noreply.github.com&gt;; 主题:&nbsp;Re: [alibaba/Sentinel] Sentinel整合Redis数据源（集群模式），RedisConnectionConfig如何构建？ (#1749)