tls: don't shadow the tls global with a local

`tls` shadows the global `tls` require, and isn't indicative of the
arument type.

PR-URL: #25861
Reviewed-By: Fedor Indutny <fedor.indutny@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

lib/_tls_wrap.js

@@ -280,19 +280,19 @@ function onerror(err) {
 
 // Used by both client and server TLSSockets to start data flowing from _handle,
 // read(0) causes a StreamBase::ReadStart, via Socket._read.
-function initRead(tls, socket) {
+function initRead(tlsSocket, socket) {
   // If we were destroyed already don't bother reading
-  if (!tls._handle)
+  if (!tlsSocket._handle)
     return;
 
   // Socket already has some buffered data - emulate receiving it
   if (socket && socket.readableLength) {
     var buf;
     while ((buf = socket.read()) !== null)
-      tls._handle.receive(buf);
+      tlsSocket._handle.receive(buf);
   }
 
-  tls.read(0);
+  tlsSocket.read(0);
 }
 
 /**