staging: lustre: add debugging ability for LFSCK

Add the ability to debug LFSCK to libcfs. This is
broken out of patch http://review.whamcloud.com/6321

.

Signed-off-by: Fan Yong <fan.yong@intel.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-2914
Reviewed-on: http://review.whamcloud.com/6321


Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>