test: check that 2nd handle.close() call is a nop

Verify that a second call to handle.close() is a no-op.

PR-URL: https://github.com/nodejs/node/pull/6395


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>