LU-9437 lfsck: handle LMV EA for migrating directory

LU-9437 lfsck: handle LMV EA for migrating directory

For the in-migration directory, its LMV EA contains not only the
LMV header, but also the FIDs for both source and target. So the
LMV EA size is larger. The lfsck_read_stripe_lmv() logic need to
handle such case properly.

Signed-off-by: Fan Yong <fan.yong@intel.com>
Change-Id: Ic43853fb5ca058042fafa0f6c81fa99d4b8d8897
Reviewed-on: https://review.whamcloud.com/31266
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Lai Siyao <lai.siyao@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>