mtree: Fix -f -f not considering type changes.

[bdrewery]

Summary

This only lists the changed type and not other attributes so that it
matches the behavior of -C as done in r66747 for fmtree. The NetBSD
-ff implementation was copied from fmtree.

MFC after: 2 weeks
Relnotes: yes

Test Plan

kyua test passes (new test fails without fix)

[imp]

I wonder why we still have fmtree though