Do something about policies_parse_exit_policy()'s arguments

  r = policies_parse_exit_policy(&line, &policy, 1, 0, 0, 1);
...
  test_assert(0 == policies_parse_exit_policy(NULL, &policy2, 1, 1, 0, 1));

Quick quiz: which of these booleans means what? And which one isn't a boolean at all? :)

(Don't work on this ticket until we merge #5528 (moved).)