LU-6052 utils: change "lfs mv" to "lfs migrate"

LU-6052 utils: change "lfs mv" to "lfs migrate"

"lfs mv" causes some confusion between mv and migration, change
"lfs mv" to "lfs migrate -m", and mark "lfs mv" deprecated.

Signed-off-by: Lai Siyao <lai.siyao@intel.com>
Change-Id: I72ead14854eb6038ba13fddec81b867bc0542b46
Reviewed-on: http://review.whamcloud.com/13754
Tested-by: Jenkins
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: frank zago <fzago@cray.com>