LU-3142 mdt: update mdt_max_mdsize in mdt_lvbo_size

LU-3142 mdt: update mdt_max_mdsize in mdt_lvbo_size

during calling mdt_lvbo_size to get the size of lsm, mdt_max_mdsize
could be less than the lsm size of this object in failover mode.
then it is needed to check and update this value.

Test-Parameters: envdefinitions=RECOVERY_MDS_SCALE_EXCEPT=failover_ost \
clientdistro=el6 serverdistro=el6 clientarch=x86_64 serverarch=x86_64 \
clientcount=4 osscount=2 mdscount=2 austeroptions=-R failover=true \
useiscsi=true testlist=recovery-mds-scale

Change-Id: Id490c346ca9f34edcc963334e396678f1b41562c
Signed-off-by: Hongchao Zhang <hongchao.zhang@intel.com>
Signed-off-by: Jian Yu <jian.yu@intel.com>
Reviewed-on: http://review.whamcloud.com/6102
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Mike Pershin <mike.pershin@intel.com>
Reviewed-by: Fan Yong <fan.yong@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>