Make NDFREE unlock VP if appropriate and not asked not to, as documented in

the manpage for namei().  This capability is not yet used attempted used
anywhere in the source tree.

sys/sys/namei.h

@@ -188,6 +188,9 @@ NDINIT(ndp, op, flags, segflg, namep, p)
 		vrele(_ndp->ni_dvp);					\
 		_ndp->ni_dvp = NULL;					\
 	}								\
+	if (!(_flags & NDF_NO_VP_UNLOCK) &&				\
+	    (_ndp->ni_cnd.cn_flags & LOCKLEAF) && _ndp->ni_vp)		\
+		VOP_UNLOCK(_ndp->ni_vp, 0, _ndp->ni_cnd.cn_proc);	\
 	if (!(_flags & NDF_NO_VP_RELE) &&				\
 	    _ndp->ni_vp) {						\
 		vrele(_ndp->ni_vp);					\