Treat all inherited file descriptors the same with --track-fds.

Treat all inherited file descriptors the same with --track-fds.

We used to special case 0, 1, 2 (stdin/out/err) specially even when
they were not inherited (anymore). Now the --track-fds=[yes|all]
option treats all inherited file descriptors the same. And if any
inherited file descriptor gets closed and reopened then they are
now treated as normal non-inherited file descriptors.

https://bugs.kde.org/show_bug.cgi?id=487296