LU-6154 zfs: striped directory and migration on ZFS

LU-6154 zfs: striped directory and migration on ZFS

1. Increase/decrease the refcount for sub_stripe object,
because we need explicitly increase/decrease refcount
for ZFS directory.

2. setup/cleanup sequence service for osd-zfs, so it can
create FID for local OSD.

3. Do not zero dah_eadata in OSD layer, instead of set it
MDD layer, so striping create process will be interferred.

4. Put 0 at the end of link data during migration, since
osd-zfs does not do it when reading link.

5. Create orphan object with linkEA data, so if migration
is interrupted, then other threads are able to read entries
from this half-migrated directory, because osd-zfs needs to
retrieve the parent FID from linkea data during read dir
entries (see osd_dir_it_rec()).

Signed-off-by: wang di <di.wang@intel.com>
Change-Id: I67cbd0b09d2716b163277425066dcf155df68039
Reviewed-on: http://review.whamcloud.com/13518
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Fan Yong <fan.yong@intel.com>
Tested-by: Jenkins
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Tested-by: Oleg Drokin <oleg.drokin@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>