test: fix old tty tests

test-tty-wrap hasn’t worked since StreamBase was introduced, I think.
test-tty-stdout-end also happens to works with PipeWrap-s.

Refs: https://github.com/nodejs/node/pull/7360
PR-URL: https://github.com/nodejs/node/pull/7613


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>