LU-7867 debugfs: fix check for out-of-bound xattr value

LU-7867 debugfs: fix check for out-of-bound xattr value

Since upsream commit 8a546777119c9c0, the validity check for in-inode
xattrs in internal_dump_inode_extra() has been incorrectly checking
the value size.  The value can go right to the end of the inode.

Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Change-Id: Id20861df7c973d76a433aecfcfd125ca32ce117b
Reviewed-on: http://review.whamcloud.com/18999
Reviewed-by: Fan Yong <fan.yong@intel.com>
Tested-by: Jenkins
Reviewed-by: Matt Ezell <ezellma@ornl.gov>