Bug in bsdinstall (fs found where not present)

[Warren Block]

>From a 9.2-PRERELEASE snapshot, go into the shell, create a GPT disk 
layout with a bunch of partitions for filesystems and swap.  Exit the 
shell and run the installer.

Go through each partition setting a mount point.  Tell bsdinstall to 
continue.  It reports that the / partition has a preexisting filesystem 
(it does not, in fact; this disk had a mishmash of MBR and NTFS on it).

Tell bsdinstall to continue anyway.  It does, and then reports that it 
can't mount /dev/ada0p2 on /mnt, presumably because, contrary to the 
misleading and incorrect error message, there is no filesystem on there.

The install fails, try again, entering all the mount points, and it will 
fail the same.

Short term solution: newfs the / partition, so there really is a 
filesystem there for bsdinstall to detect and warn about.  Then it 
works.