Fix ability to disable TCP timeouts with setTimeout(0)

lib/net.js

@@ -937,6 +937,8 @@ Stream.prototype.setTimeout = function (msecs) {
   if (msecs > 0) {
     timeout.enroll(this, msecs);
     if (this.fd) { timeout.active(this); }
+  } else if (msecs === 0) {
+    timeout.unenroll(this);
   }
 };