SSH Support for FS devices

[yaleneyoung]

Please help to review this PR, thank you very much.

Who are we
FS is a global cross-industry network solutions provider in the ICT field, providing full-process services for global data centers, telecoms and all types of enterprises with products and solutions. Our platform is located at fs.com (https://www.fs.com/)
Our broad array of products and services range from hardware and software to integrated IT communications solutions such as security, cloud, hybrid infrastructure, and digital experience. Through highly integrated digital platforms, we can tailor the best solutions to different industry customers in depth according to customer scenarios, helping customers solve various problems in IT network construction, and empowering customers'business decisions.

Why I did it
SSH Support for FS devices

[ktbyers]

@yaleneyoung I apologize for the delay in getting to this.

Can you add the config and show test output to this PR (i.e. run the tests and post the output here)?

https://github.com/ktbyers/netmiko/blob/develop/TESTING.md

[ktbyers]

Also you forgot to add the telnet driver into ssh_dispatcher.py and have a few minor linting errors.