Xserver: Removed rules that allowed xdm_t to use systemd_logind

Xserver: Removed rules that allowed xdm_t to use systemd_logind
/run/systemd/sessions/.* fifo_file descriptor, as that access is now
added to authlogin_pgm_domain (which xdm is)

The following calls in authlogin_pgm_domain are optional ( you may be
using upstart or sysvinit or whatever and my not have the systemd module
installed )

systemd_use_fds_logind($1)
systemd_write_inherited_logind_sessions_pipes($1)