async mode for installs, upgrades

[Chris Cappuccio <chris_(_at_)_dqc_(_dot_)_org>]

The install disk uses async mode for installs, and for upgrades,

Considering that an accidental crash with async mounts can destroy your
filesystems, shouldn't the upgrade script stick with the default of 
synchronous mounts?

(Since an upgrade affects a filesystem that has been in use, and may take
significant effort to restore from backups [or worse from scratch], while an
install can be done over with just a little loss of time..)

-chris