LU-4955 lfsck: reset param when the LFSCK is reset

LU-4955 lfsck: reset param when the LFSCK is reset

If "--reset" or "-r" is specified when start the LFSCK manually,
then all non-specified parameters will be set as default values.

If the former LFSCK instance completed, then when re-trigger the
LFSCK, it will restart from the beginning, and all non-specified
parameters will be set as default values.

Change the "window" option in lfsck_start to "window_size".

Update the lctl manpage for LFSCK.

Signed-off-by: James Nunez <james.a.nunez@intel.com>
Signed-off-by: Fan Yong <fan.yong@intel.com>
Change-Id: I5b1d7dd2507ab2f50e152f5a839bf9544a9dc255
Reviewed-on: http://review.whamcloud.com/10091
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-by: Lai Siyao <lai.siyao@intel.com>