install/53785: install media fails when root is autoconfigured from existing raid

[bad%bsd.de@localhost]

>Number:         53785
>Category:       install
>Synopsis:       GENERIC on install media sets root fs to raid0a
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    install-manager
>State:          open
>Class:          change-request
>Submitter-Id:   net
>Arrival-Date:   Thu Dec 13 15:00:00 +0000 2018
>Originator:     Christoph Badura
>Release:        NetBSD 8.99.27
>Organization:
Bozotic Software Testing Labs
	
>Environment:
	
	
System: NetBSD 8.99.27 as of 2018-12-12
Architecture: amd64
Machine: amd64
>Description:
The GENERIC kernel on the install media has RAID autoconfiguration
turned on.  When booted on a machine that has a RAID set configured with
"-A root" it will select the RAID set as root device and not boot into
the installer.

Not that this is not specific to current but was introduced with switching
the install media to GENERIC kernels.

	
>How-To-Repeat:
Install NetBSD onto a RAID set.
raidctl -A root raid0
reboot from e.g. NetBSD-8.99.27-amd64.iso.
	
>Fix:
	

>Unformatted: