LU-4813 lfsck: reuse OUT_PORTAL for orphan iteration

LU-4813 lfsck: reuse OUT_PORTAL for orphan iteration

It is unnecessary to use independent request portal for LFSCK
orphan iteration, which will cause trouble for UT work in the
future and also may cause interoperability issues. So we will
reuse the existing OUT_PORTAL for the same purpose.

Signed-off-by: Fan Yong <fan.yong@intel.com>
Change-Id: I721977adb58ef35651775bacab6b5f9e325eb26a
Reviewed-on: http://review.whamcloud.com/9772
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-by: Mike Pershin <mike.pershin@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>