LU-448 add lst stat --count

LU-448 add lst stat --count

This adds lst stat --count, making it easier to script up data
collection for performance tests.

The patch is from Oracle bug 22638 attachment 33001

Change-Id: Ic60e6226ce85ebbc2d314e41c7e85ba5879ea64e
Signed-off-by: Wally Wang <wang@cray.com>
Reviewed-on: http://review.whamcloud.com/1312
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Liang Zhen <liang@whamcloud.com>
Reviewed-by: Lai Siyao <laisiyao@whamcloud.com>
Reviewed-by: Johann Lombardi <johann@whamcloud.com>