tls: reduce TLS 'close' event listener warnings

Without this, some heavy usage of TLS sockets can result in
MaxListenersExceededWarning firing, from the 'this.on('close', ...)'
line here.

These appear to come from reinitializeHandle, which calls _wrapHandle
repeatedly on the same socket instance.

lib/_tls_wrap.js

@@ -713,7 +713,12 @@ TLSSocket.prototype._wrapHandle = function(wrap, handle, wrapHasActiveWriteFromP
   this[kRes] = res;
   defineHandleReading(this, handle);
 
-  this.on('close', onSocketCloseDestroySSL);
+  // Guard against adding multiple listeners, as this method may be called
+  // repeatedly on the same socket by reinitializeHandle
+  if (this.listenerCount('close', onSocketCloseDestroySSL) === 0) {
+    this.on('close', onSocketCloseDestroySSL);
+  }
+
   if (wrap) {
     wrap.on('close', () => this.destroy());
   }