LU-4684 migrate: pack lmv ea in migrate rpc

LU-4684 migrate: pack lmv ea in migrate rpc

To support stripe directory migration, pack lmv_user_md in migrate
RPC. Add arguments of 'mdt-count' and 'mdt-hash' for 'lfs migrate'.

Disable directory migration related tests temprorily, and we'll
enable them later in the last patch of this set.

Signed-off-by: Lai Siyao <lai.siyao@whamcloud.com>
Change-Id: I914a9205a1a558da8c4231e7c83334621b5c92c0
Reviewed-on: https://review.whamcloud.com/31424
Tested-by: Jenkins
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Fan Yong <fan.yong@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>