LU-9324 lfs: output stripe info in YAML format

LU-9324 lfs: output stripe info in YAML format

Add --yaml|-y for lfs getstripe to output plain/PFL layout file's
stripe information in YAML format.

Signed-off-by: Bobi Jam <bobijam.xu@intel.com>
Change-Id: Ic6a3bf3572346f06ed90f75945acf374efd0fd96
Reviewed-on: https://review.whamcloud.com/26708
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Niu Yawei <yawei.niu@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>