This patch adds an interface to manage systemd_passwd_var_run_t symlinks that
I'll add another patch to use shortly.
It has a number of changes needed by systemd_logind_t to set permissions for
local logins.
It has some more permissions that systemd_machined_t needs, I don't think it's
everything that systemd_machined_t needs but it's a start.
It has some changes for udev_t for systemd-udevd.
60114027f7