tls: set servername on client side too

Backport-PR-URL: #18050
Backport-PR-URL: #20456
PR-URL: #17935
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: Sebastiaan Deckers <sebdeckers83@gmail.com>
Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>

lib/_tls_wrap.js

@@ -628,7 +628,7 @@ TLSSocket.prototype._finishInit = function() {
     this.alpnProtocol = this.ssl.getALPNNegotiatedProtocol();
   }
 
-  if (process.features.tls_sni && this._tlsOptions.isServer) {
+  if (process.features.tls_sni) {
     this.servername = this._handle.getServername();
   }