LU-2435 osd-zfs: use zfs native dnode accounting

LU-2435 osd-zfs: use zfs native dnode accounting

If ZFS userobj_accounting feature exists, use it for osd-zfs object
accounting; otherwise estimate object use by block space.

Disable quota check in conf-sanity:32b and sanity-quota:7e if the
underlying zfs version is below 0.7.0. For conf-sanity test, if the
running ZFS is version 0.7.0 or higher, upgrade the zpool image to
enable native dnode accounting. That ensures we also test the upgrade
procedure.

Test-Parameters: mdtfilesystemtype=zfs ostfilesystemtype=zfs testlist=sanity-quota,sanity-quota,sanity-quota,conf-sanity,conf-sanity envdefinitions=SLOW=yes
Change-Id: I0fe47fd0e3d787663a4c72fd708678827fdfb474
Signed-off-by: Jinshan Xiong <jinshan.xiong@intel.com>
Reviewed-on: https://review.whamcloud.com/15294
Tested-by: Jenkins
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>