Revert r285018, r285019, r285076, r285078, r285082.

The true cause of the missing UFS/MSDOSFS labels has been
identified, and only affects stable/10 at the moment.

An request for commit to stable/10 will be pending RE approval
after this commit.

MFC after: 1 day
X-MFC-Note: never
X-MFC-Never: r285018, r285019, r285076, r285078, r285082
Sponsored by: The FreeBSD Foundation