LU-2990 osd-zfs: locate cursor to specified pos via load API

There was defect for zfs-based backend when traverse directory:
the dt_iteration API ::load() did not locate the cursor to the
specified position, then caused non-first directory readpage
RPC obtained repeated entries, and then caused readdir() loop
or unexpected dir hash collision.

Signed-off-by: Fan Yong <fan.yong@intel.com>
Change-Id: I9c159f0f80677590869246dd9f30f0dfb9cc2fbc
Reviewed-on: http://review.whamcloud.com/5894
Tested-by: Hudson
Reviewed-by: Li Wei <wei.g.li@intel.com>
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
LU-2267 osd-zfs: Use appropriate ZFS flags for file attributes

Instead of setting arbitrary bits in pflags, convert to use existing
ZFS attributes.  This format is different from previous implementation
and will cause older filesystems with attrs set to not behave
correctly.

Signed-off-by: Nathaniel Clark <nathaniel.l.clark@intel.com>
Change-Id: Ia0aac3e12adedd95b215f93ebe538a61abf910fa
Reviewed-on: http://review.whamcloud.com/5988
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>