MFC r303631:

MFC r303631:

Fix non-functional bsdinstall services dialog.

The most recent version of bsdinstall does not seem to respect any of
the checkboxes in the "Choose the services you would like to be started
at boot" dialog.  None of the chosen services end up in the rc.conf file
that is installed onto the target system.

This is caused by the bsdinstall/scripts/hardening script, which
implements the new hardening options dialog.  The script starts by
overwriting the previously written rc.conf.services file:

    echo -n > $BSDINSTALL_TMPETC/rc.conf.services

which is obviously incorrect.  It should clear out rc.conf.hardening
instead.

Approved by:	re (kib)
Reviewed by:	allanjude
PR:		211506
Differential Revision: https://reviews.freebsd.org/D7387