servername param added for Servername Indication

[iamrc90]

@ditesh ,

Recently while working on Node 14, I faced an error with Gmail Accounts in production.

self signed certificate
    at TLSSocket.onConnectSecure (_tls_wrap.js:1497:34)
    at TLSSocket.emit (events.js:315:20)
    at TLSSocket._finishInit (_tls_wrap.js:932:8)
    at TLSWrap.ssl.onhandshakedone (_tls_wrap.js:706:12) {
  code: 'DEPTH_ZERO_SELF_SIGNED_CERT'
}

Referring to issue https://github.com/nodejs/node/issues/28167 and from the node js documentation (https://nodejs.org/docs/latest-v14.x/api/tls.html), SNI ( server name identification ) needs to be passed when connecting to Gmail pop3 server, which used to be sent by default before node 12. I have passed the parameter servername to the tls.connect() method to fix my problem.

You are requested to have a look at the PR and suggest if it can be merged. Thanks