LU-5914 lfsck: dt_lookup() LBUG

LU-5914 lfsck: dt_lookup() LBUG

This patch contains two fixes:
1. object can be remote in lfsck_namespace_rebuild_linkea(), remove
   assert on this.
2. initialize dt_index_ops for parent in l_n_verify_stripe_slave()
   before dt_lookup() on it.

Signed-off-by: Lai Siyao <lai.siyao@intel.com>
Change-Id: I0755f471470cc0805db222640bba1d04f4128388
Reviewed-on: http://review.whamcloud.com/13188
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Fan Yong <fan.yong@intel.com>
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>