filefrag: support PFL and FLR file

filefrag: support PFL and FLR file

Add FIEMAP_EXTENT_DATA_MIRROR support FLR file, which is returned
from Lustre indicating that a new mirror will be processed, so we'd
reset the fm_start and fe_logical.

Change-Id: Ifa68d951ac68d9f141eae915e58c13d73833c8c9
Signed-off-by: Bobi Jam <bobijam@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/40765
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Wang Shilong <wshilong@whamcloud.com>
Tested-by: Andreas Dilger <adilger@whamcloud.com>