test: Revert add option to use node in path

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• commit message follows commit guidelines

Affected core subsystem(s)

tools

Description

This reverts commit 4198253a, landed in https://github.com/nodejs/node/pull/9674.

This fails at

File "tools/test.py", line 1429, in ProcessOptions options.j = int(cores) if cores is not None else multiprocessing.cpu_count()

with the error

NotImplementedError: cannot determine number of cpus

from

File "...multiprocessing/init.py", line 136, in cpu_count raise NotImplementedError('cannot determine number of cpus')

on MacOS machines.