Leaks /etc/os-release fd to child processes

[Vogtinator]

This library is often loaded into application launchers. However, once as_distro_details_new is called, the fd never gets closed as O_CLOEXEC is not set as flag.
For instance, open a terminal from krunner and you'll see that fd 23 of /proc/self/fd is valid and points to /etc/os-release.

[ximion]

There is indeed a leak on the data input stream there (which I guess triggers this issue). Adjusting the flags might also be a good idea.