LU-5117 lfsck: naming rules for orphan

LU-5117 lfsck: naming rules for orphan

The rules for naming orphan under /ROOT/.lustre/lost+found/MDTxxxx/
are as following:

1) The orphan's name should start with the "FID" to simplify the
   sorting by FID.

2) The name needs to contain the orphan type to indicate why the
   orphan is created.

3) To resolve the name conflict, there is the conflict version
   in the name.

4) There can be infix in the name to indicate more information,
   such as its original name, the original stripe offset, etc.

So the name will be like:
${FID}-${infix}-${type}-${conflict_version}

Signed-off-by: Fan Yong <fan.yong@intel.com>
Change-Id: I6eaa0daff39729f401a4f45eae4c1efdd527275a
Reviewed-on: http://review.whamcloud.com/10482
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Lai Siyao <lai.siyao@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>