LU-12127 lfsck: skip orphan processing for namespace LFSCK

LU-12127 lfsck: skip orphan processing for namespace LFSCK

LFSCK can reconnect a recently-deleted orphan object back
into the normal namespace when it shouldn't. This can cause
access to the deleted data (potential security risk), and
sometimes cause an assertion if orphan is later deleted.

The commit 077570483e75e0610fd45149b926097547c434b8 skips
the orphan object during LFSCK scan. But what needs to be
skipped is only the namespace LFSCK logic for the orphan
object, but the layout LFSCK processing is still necessary
for the orphan object to verify the consistency between the
orphan MDT-object and related OST-object(s). This patch
just does that.

Signed-off-by: Fan Yong <fan.yong@intel.com>
Change-Id: I9b2809b95efa4b3c3e3b2c7d0a501624ed3ebbe5
Reviewed-on: https://review.whamcloud.com/34174
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Hongchao Zhang <hongchao@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>