LU-4008 mdt: Use actual size for layout lock intents

LU-4008 mdt: Use actual size for layout lock intents

The intent for layout looks up the size of the lov xattr. That size
should be used for the reply buffer instead of the maximum size ever
seen.

Lustre-commit: 586a609c9d5a53e75174b66269c685f594ded7c2
Lustre-change: http://review.whamcloud.com/#/c/9571

Signed-off-by: Matt Ezell <ezellma@ornl.gov>
Signed-off-by: James Simmons <uja.ornl@gmail.com>
Change-Id: Id5d560001df3d058d189339ede33347f8353990a
Reviewed-on: http://review.whamcloud.com/10018
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-by: Mike Pershin <mike.pershin@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>