test: use tmp directory in chdir test

This patch

 - makes chdir test to use the tmp directory
 - moves the test to parallel
 - renames the file to test-process-chdir as chdir is in process module

PR-URL: https://github.com/nodejs/node/pull/2589


Reviewed-By: Brendan Ashworth <brendan.ashworth@me.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>