LU-1866 lfsck: LFSCK 1.5 user space control

LU-1866 lfsck: LFSCK 1.5 user space control

Include the user space command to start/stop the LFSCK for
namespace consistency check and repair. And proc interface
to query the LFSCK status, statistical informtion, and ect.

Test-Parameters: envdefinitions=ENABLE_QUOTA=yes testlist=sanity-lfsck

Signed-off-by: Fan Yong <fan.yong@intel.com>
Change-Id: Icf4046b313dc1653b5b8b1a3add7fa0329ca7ad0
Reviewed-on: http://review.whamcloud.com/4911
Tested-by: Hudson
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Jian Yu <jian.yu@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>