Due to cryptsetup being parallel with this initially, we need this to support LVM/MD on LUKS.

Writing /.autorelabel from fedora-autorelabel does not work because the
script is executed only if relabel was already requested.

Create a new unit fedora-autorelabel-mark.service which will be
responsible for creating /.autorelabel if SELinux is disabled.
The unit takes advantage of the new "ConditionSecurity=" support in
systemd.

The old script checked for a read-only filesystem first. The new unit
does not do that. If / is read-only, touch will simply fail. This should
not be considered as a failure of the unit, so "-" is used in ExecStart.

There have been arguments on systemd-devel that the root directory
should not be abused for flag files like /.autorelabel. It has a long
tradition in Fedora though (since 2005). Maybe we can change it
eventually, but let's keep it where it is for now.

The service unit file already checks whether /.autorelabel or the
"autorelabel" parameter are present. No need to recheck in the script.
Using the new "ConditionSecurity=" feature systemd can also check
whether SELinux is enabled.

Currently both are started early during boot and in the best case
are no-op, in the worst - hack is executed after unhack and leaves
/dev/.in_sysinit hanging around forever. Make sure unhack is executed
after hack and after sysinit.target as name suggests.

Signed-off-by: Andrey Borzenkov <arvidjaar@gmail.com>