Revert "vnode: Rework vput() to avoid holding the vnode lock after decrementing"

The change can introduce a deadlock if we release the vnode lock in
order to release a reference, and then end up releasing the final
reference after all, requiring a relock of the vnode. This relock may
violate the usual parent->child vnode lock order.

This reverts commit 99cb3dca4773fe4a16c500f9cb55fcd62cd8d7f3.

Reported by: jhb