LU-4712 llite: lock the inode to be migrated

LU-4712 llite: lock the inode to be migrated

Because the inode and its connected dentries will be cleared
out of the cache after migration, the inode needs to be locked
during the migration.

Signed-off-by: wang di <di.wang@intel.com>
Change-Id: Ibbbb33473de1a67df85ef8930debcf22cd775bcb
Reviewed-on: http://review.whamcloud.com/9689
Tested-by: Jenkins
Reviewed-by: Lai Siyao <lai.siyao@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Fan Yong <fan.yong@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>