Fix mtree for usr/

MFC after: 3 days

(cherry picked from commit 695052e240c7c4291707a55358fe79de9ef79767)

Account for missing `..' in BSD.usr.dist for clang 14.0.3.

MFC after: 3 days

(cherry picked from commit 1d25053e9365e99a2d16f2ee64d3416f14f7f167)

Remove yet another incorrect .. level from BSD.usr.dist

Since the spacing was off, it was not clear that it descended one level
too many.

Fixes: 695052e240c7
MFC after: 3 days

(cherry picked from commit 987d26ee3f7a1685f7070db834478964170b6f62)