LU-2733 osd: not return "-ENOENT" for zfs osd_object_init

For zfs backend, the osd_object_init() should not return
"-ENOENT" if osd_fid_lookup() cannot find the object,
which is normal for new created cases.

Signed-off-by: Fan Yong <fan.yong@intel.com>
Change-Id: I76e5d802d0caf8ac3a9992278ec2f7c6c6e2cf07
Reviewed-on: http://review.whamcloud.com/5242
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Tested-by: Hudson
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>