GEOM_RAID in GENERIC is harmful

[Eugene Grosbein]

Hi!

9-STABLE has got options GEOM_RAID in GENERIC.
In real world, this change is pretty harmful and there are lots of cases
when 9.0-RELEASE systems upgraded to 9-STABLE fail to mount root UFS filesystem
or attach ZFS.

It seems, there are lots of HDDs supplied with pseudo-RAID labels at the end:
pre-installed Windows machined having motherboards with pseudo-RAID
like Intel RapidStore and alike. One can not even be aware of these labels.

9.0-RELEASE can be installed on such HDDs and use them with GMIRROR or ZFS
without a problem. Upgraded to 9-STABLE, such system fails to build due
to GRAID jumping out of box and grabbing HDDs for itself,
so GMIRROR or ZFS got broken.

That's makes users very angry when production server fails to boot
with GENERIC kernel after correctly performed upgrade.

GEOM_RAID compiled in GENERIC should be deactivated and require activation
with some loader knob. Also, we need distinct RELEASE NOTES warning about the issue.

Eugene Grosbein