MFC r208773:

MFC r208773:
Sometimes vnodes share the lock despite being different vnodes on
different mount points, e.g. the nullfs vnode and the covered vnode
from the lower filesystem. In this case, existing assertion in
vop_rename_pre() may be triggered.

Check for vnode locks equiality instead of the vnodes itself to
not trip over the situation.

git-svn-id: svn://svn.freebsd.org/base/stable/8@209293 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f