LU-5391 osd-zfs: ZAP object block sizes too small

LU-5391 osd-zfs: ZAP object block sizes too small

Currently osd-zfs ZAP objects use 4K for both leaf
and indirect blocks. This patch increases:
- leaf block to 16K, which equals ZFS fzap_default_block_shift
- indirect block to 16K, the default used by ZPL directories

Signed-off-by: Isaac Huang <he.huang@intel.com>
Change-Id: I5b476414d27822a14afb25e1307991fbd2e3a59e
Reviewed-on: http://review.whamcloud.com/11182
Tested-by: Jenkins
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Mike Pershin <mike.pershin@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>