LU-6895 lfsck: not destroy directory when fix FID-in-dirent

LU-6895 lfsck: not destroy directory when fix FID-in-dirent

When repair FID-in-dirent, the lfsck may append the FID after
the name entry directly. If checking the space after the name
entry improperly, it may over write the subsequent name entry
as to crash the whole directory.

Test-Parameters: alwaysuploadlogs envdefinitions=SLOW=yes,ENABLE_QUOTA=yes mdtfilesystemtype=ldiskfs mdsfilesystemtype=ldiskfs ostfilesystemtype=ldiskfs clientdistro=el7 ossdistro=el7 mdsdistro=el7 mdtcount=1 testlist=sanity-lfsck,sanity-lfsck,sanity-lfsck,sanity-lfsck
Signed-off-by: Fan Yong <fan.yong@intel.com>
Change-Id: Ia1afc643fdfac205a5ea7aa9c365e45b4da90868
Reviewed-on: http://review.whamcloud.com/16440
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: Oleg Drokin <oleg.drokin@intel.com>