src: fix memory leak in fs.writeSync error path

The SYNC_CALL macro returns on error, bypassing the delete[] call.

Mea culpa, it looks like I introduced this memory leak back in 2013,
in commit d2b80b8a ("src: clean up FSReqWrap").

PR-URL: https://github.com/iojs/io.js/pull/1092


Reviewed-By: Fedor Indutny <fedor@indutny.com>