Update base.py for support ipv6

[deng-ruixuan]

connection support ipv6.
eg:
ipv6 url should be:
[fe80:xx::89]:9200

[elasticmachine]

Since this is a community submitted pull request, a Jenkins build has not been kicked off automatically. Can an Elastic organization member please verify the contents of this patch and then kick off a build manually?

[cla-checker-service]

❌ Author of the following commits did not sign a Contributor Agreement:
c80b7db

Please, read and sign the above mentioned agreement if you want to contribute to this project

[sethmlarson]

Thanks for this, could you sign the CLA and add a few test cases?

[sethmlarson]

Closed in favor of #1460