test: test sending a handle twice

Added [test-cluster-send-handle-twice.js](https://github.com/kunnix/node/blob/80b2557c513ff6d682e6a0fba728bfd462e17fc5/test/simple/test-cluster-send-handle-twice.js) testing to send a handle twice to the parent process.

This currently leads to a crash on Linux 32-bit (Ubuntu), see [issue 5469](https://github.com/joyent/node/issues/5469).