Remove dead code

Garret is not as pedantic as he was before.

Moreover since we now have a function to propagate exit value from a
child process, limited amount of tst_* functions can be used in child
processes as well.

Signed-off-by: Garrett Cooper <yanegomi@gmail.com>
Signed-off-by: Cyril Hrubis <chrubis@suse.cz>