don't check fs_flags for _FLAGS_UPDATED as it is stored in fs_old_flags..
If you had a UFS2 FS that didn't have it's super block at SBLOCK_UFS2,
you'll end up corrupting your FS as the superblock is updated and written
to a different location...

makefs used to put the superblock at SBLOCK_UFS1 for UFS 2 FS's causing
this issue...

Reviewed by:	silience from mckusick
MFC after:	1 week