LU-7660 dne: support fs default stripe

LU-7660 dne: support fs default stripe

On DNE system slave MDTs should honor fs default stripe, to achieve
this, slave MDT should lock fs root, and cache XATTR_NAME_LOV, below
functionalities are added for this:
* take and cache remote root XATTR lock on slave MDTs.
* add dt_invalidate operation to invalidate OSP attributes cache,
  normally it's called in mdt_object_unlock(), but if we cache this
  lock, it's called upon cross-MDT lock cancel.
* enable OSP attribute cache by default.
* migrate should invalidate remote target explictely if it's newly
  created, because it doesn't take its lock beforehand.
* OSP should cleanup ldlm namespace in device cleanup because there
  may be cached locks.
* add sanity.sh 405 test for this.

Signed-off-by: Lai Siyao <lai.siyao@intel.com>
Change-Id: I90e5f35f3b6a294a2a559c28df267f92ce188b9c
Reviewed-on: http://review.whamcloud.com/19041
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>