LU-4767 lfsck: sub-task thread should not change lc_link

LU-4767 lfsck: sub-task thread should not change lc_link

The lfsck sub-task thread (for double scan) should not change the
"lfsck_component:lc_link" which may cause the master lfsck engine
thread to access some unexpected RAM space by race.

LFSCK should not return -ENODEV to avoid to misguide ptlrpc.

Signed-off-by: Fan Yong <fan.yong@intel.com>
Change-Id: Ifb80eaf7c1c4ba9bf7fbd5213e9eae09efed7e28
Reviewed-on: http://review.whamcloud.com/9661
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Lai Siyao <lai.siyao@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>