LU-10287 flr: lfs mirror verify command

LU-10287 flr: lfs mirror verify command

This patch adds "lfs mirror verify" command to verify
that each SYNC mirror of a mirrored file contains exactly
the same data. It supports specifying multiple mirrored
files in one command line.

Usage:

lfs mirror verify [--only <mirror_id,mirror_id2[,...]>]
		  [--verbose|-v]
		  <mirrored_file> [<mirrored_file2> ...]

Options:

--only <mirror_id,mirror_id2[,...]>
Only verify the mirrors specified by mirror_ids contain
exactly the same data. This option cannot be used when
multiple mirrored files are specified.

--verbose|-v
With this option, the command will print where the
differences are if the data do not match. Otherwise,
the command will just return an error in that case.

Test-Parameters: testlist=sanity-flr
Signed-off-by: Jian Yu <jian.yu@intel.com>
Change-Id: Ib436dea73a8e7a0f8e30b246bb0062023a97cb81
Reviewed-on: https://review.whamcloud.com/30387
Tested-by: Jenkins
Reviewed-by: Jinshan Xiong <jinshan.xiong@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>