LU-6361 lfsck: measure LFSCK 4 performance

LU-6361 lfsck: measure LFSCK 4 performance

Measure the performance of namespace LFSCK for routine-check
cases and repairing cases under kinds of DNE configurations.

It also measures how much the namespace LFSCK will affect the
performance of creating small files.

Test-Parameters: mdtcount=4 mdscount=2 mdtfilesystemtype=ldiskfs mdsfilesystemtype=ldiskfs ostfilesystemtype=ldiskfs envdefinitions=SLOW=yes testlist=lfsck-performance
Signed-off-by: Fan Yong <fan.yong@intel.com>
Change-Id: I4f510b946d9d779fabcdec0ecd8e6c65278eb875
Reviewed-on: http://review.whamcloud.com/12109
Tested-by: Jenkins
Reviewed-by: Jian Yu <jian.yu@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>