tls: handle `error` events with `_tlsError`

Previously `TLSSocket#_emitTLSError` was used as an `error` event
handler. However that function can emit `error` event itself, so it is
not suitable for such use. Luckily the event can be emitted only when
the control is released, so this looping-error can't happen.

Replace the error handler for clarity and correctness.

PR-URL: https://github.com/nodejs/node/pull/8889
Reviewed-By: Franziska Hinkelmann <franziska.hinkelmann@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

lib/_tls_wrap.js

@@ -272,7 +272,7 @@ function TLSSocket(socket, options) {
   // Proxy for API compatibility
   this.ssl = this._handle;
 
-  this.on('error', this._emitTLSError);
+  this.on('error', this._tlsError);
 
   this._init(socket, wrap);
 
@@ -554,7 +554,7 @@ TLSSocket.prototype._releaseControl = function() {
   if (this._controlReleased)
     return false;
   this._controlReleased = true;
-  this.removeListener('error', this._emitTLSError);
+  this.removeListener('error', this._tlsError);
   return true;
 };