staging: lustre: obdclass: change object lookup to no wait mode

staging: lustre: obdclass: change object lookup to no wait mode

Currently we set LU_OBJECT_HEARD_BANSHEE on object when we want
to remove object from cache, but this may lead to deadlock, because
when other process lookup such object, it needs to wait for this
object until release (done at last refcount put), while that process
maybe already hold an LDLM lock.

Now that current code can handle dying object correctly, we can just
return such object in lookup, thus the above deadlock can be avoided.

Signed-off-by: Lai Siyao <lai.siyao@intel.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-9049
Reviewed-on: https://review.whamcloud.com/26965
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Tested-by: Cliff White <cliff.white@intel.com>
Reviewed-by: Fan Yong <fan.yong@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: NeilBrown <neil@brown.name>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>