MFC: r235508

Fix a couple of issues that appear to be inherited from the old
8.x code:

• If the lock cannot be acquired immediately unlocks 'bar' vnode

and then locks both vnodes in order.

• wrong vnode type panics from cache_enter_time after calls by

ext2_lookup.

The fix merges changes from ufs/ufs_lookup.c.

Submitted by: Mateusz Guzik
Approved by: jhb (mentor)