LU-7502 utils: add --mdt-count & --mdt-hash options

LU-7502 utils: add --mdt-count & --mdt-hash options

    lfs find --mdt-count and --mdt-hash options
    lfs getdirstripe --mdt-count and --mdt-hash options

Signed-off-by: Yang Sheng <yang.sheng@intel.com>
Change-Id: I55f2d7660c4e4fea5a197a57407b614c4004974c
Reviewed-on: https://review.whamcloud.com/25515
Tested-by: Jenkins
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Reviewed-by: Jian Yu <jian.yu@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>