phpstan-flycheck will block phpmd and phpcs from running.

I'm not sure if this is an issue with flycheck or the phpstan-flycheck

the other php flychecks don't run.

``` emacs-lisp
(flycheck-add-next-checker 'php 'phpstan)
```
That pretends it to the list of next checkers for php.

but even if I change it to append it still doesn't work. It will run all the other checkers but not get to phpspec.

If I modify `flycheck.el` and manually add phpstan to `next-checkers` of `php` **and** `php-cs`.

Then it works. It seems like flycheck doesn't honor the next-checkers list and they know it.