UBUNTU: SAUCE: overlayfs: fix regression in whiteout detection

The Ubuntu backport of the below commit necessarily had to follow the
changes to is_ovl_whiteout.  In the process the wrong dentry was passed
preventing correct detection of legacy whitouts in a rename over a
whitout on some upper filesystem types (at least ramfs):

  commit 11f37104
  Author: Miklos Szeredi <mszeredi@redhat.com>
  Date:   Mon Mar 21 17:31:44 2016 +0100

    ovl: verify upper dentry before unlink and rename

Pass the correct dentry to allow detection of the appropriate whiteout
types.

Fixes: 11f37104 ("ovl: verify upper dentry before unlink and rename") in Ubuntu
BugLink: http://bugs.launchpad.net/bugs/1618572


Signed-off-by: Andy Whitcroft <apw@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>