LU-10055 mdt: use max_mdsize in reply for layout intent

LU-10055 mdt: use max_mdsize in reply for layout intent

The LAYOUT intent reply LVB buffer size is set to a current
file layout, meanwhile it is not working when layout is changed
and the mdt_max_mdsize is better to use as size of reply buffer.
This buffer will be shrinked to the new layout size after all.

Without that change the new layout size may be bigger and layout
is not returned back, causing extra RPC from client.
The mdt_lvbo_fill() is changed also to update mdt_max_mdsize if
larger layout is found. The related message level is decreased
from D_ERROR to D_INFO.

Signed-off-by: Mikhal Pershin <mike.pershin@intel.com>
Change-Id: Iaac5dcb8b4c5aa2c050dddb5b3fb2662c59f133b
Reviewed-on: https://review.whamcloud.com/30004
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Jinshan Xiong <jinshan.xiong@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>