LU-9771 flr: lfs mirror resync command

LU-9771 flr: lfs mirror resync command

This patch adds "lfs mirror resync" command to resynchronize a
mirrored file.

Usage:

lfs mirror resync [--only <mirror_id[,...]>] <mirrored file>

Options:

--only <mirror_id[,...]>
	Indicates which mirror(s) specified by mirror_id(s) needs to
	be resynchronized. The mirror_id is the numerical unique
	identifier for a mirror. Multiple mirror_ids are separated
	by comma.

Test-Parameters: testlist=sanity-flr
Signed-off-by: Bobi Jam <bobijam.xu@intel.com>
Change-Id: Ic2aa474d1023a4364aa9d90c59120b1d5c89a269
Signed-off-by: Jinshan Xiong <jinshan.xiong@intel.com>
Reviewed-on: https://review.whamcloud.com/29243
Tested-by: Jenkins
Reviewed-by: Bobi Jam <bobijam@hotmail.com>
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>