test: use strict assertions in module loader test

Replace calls to assert.equal() and assert.notEqual() with
assert.strictEqual() and assert.strictNotEqual() respectively.

PR-URL: https://github.com/nodejs/node/pull/9263


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>