test: reduce brittleness of tab complete test

test-repl-tab-complete includes tests that ensure that certain keys do
not appear in tab completions or that completion does not crash the
repl. It performed these tests by comparing completion output to a
hardcoded list of expected keys. This list is made incorrect by any api
changes that occur when new versions of V8 are introduced.

With this change, we assert that the specific keys to be avoided are
not present in the output instead.

PR-URL: https://github.com/nodejs/node/pull/5772


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

Conflicts:
	test/parallel/test-repl-tab-complete.js