tls: set servername on client side too

PR-URL: https://github.com/nodejs/node/pull/17935


Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: Sebastiaan Deckers <sebdeckers83@gmail.com>
Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>