tools, test: update test-npm-package paths

Makes the same changes as
https://github.com/nodejs/node/commit/994617370e8e66f3ea9488fec32fd912e7902396
to update the test runner for npm5.

PR-URL: https://github.com/nodejs/node/pull/13441
Refs: https://github.com/nodejs/node/pull/12936


Reviewed-By: Jan Krems <jan.krems@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>