Make guard run_all after previously failing tests pass

This is related to the changes in https://github.com/modeset/teaspoon/pull/173 and helps to fix https://github.com/modeset/guard-teaspoon/issues/3.

I should also note that this problem was more than just not running all tests on success. This also fixes the problem that guard-teaspoon could not re-run all tests after it had run tests on a modified file because that file would keep being re-run instead.