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.
Refs: https://github.com/nodejs/node/pull/12936
Checklist
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make -j4 test
(UNIX), orvcbuild test
(Windows) passes -
commit message follows commit guidelines
Affected core subsystem(s)
tools, test