MFV r302653: 6111 zfs send should ignore datasets created after the ending snapshot

MFV r302653: 6111 zfs send should ignore datasets created after the ending snapshot

illumos/illumos-gate@4a20c933b148de8a1c1d3538391c64284e636653
https://github.com/illumos/illumos-gate/commit/4a20c933b148de8a1c1d3538391c64284
e636653

https://www.illumos.org/issues/6111
  If you create a zfs child folder, zfs send returns an error when a recursive
  incremental send is done between two snapshots made prior to the folder
  creation.
  The problem can be reproduced with the following steps.
  root@zfs:/# zfs create pool/test
  root@zfs:/# zfs snapshot pool/test@snap1
  root@zfs:/# zfs snapshot pool/test@snap2
  root@zfs:/# zfs create pool/test/child
  root@zfs:/# zfs send -R -I pool/test@snap1 pool/test@snap2 > /dev/null
  WARNING: could not send pool/test/child@snap2: does not exist
  WARNING: could not send pool/test/child@snap2: does not exist
  root@zfs:/# echo $?
  1
  root@zfs:/# zfs snapshot -r pool/test@snap3
  root@zfs:/# zfs send -R -I pool/test@snap1 pool/test@snap3 > /dev/null
  root@zfs:/# echo $?
  0
  root@zfs:/# zfs send -R -I pool/test@snap2 pool/test@snap3 > /dev/null
  root@zfs:/# echo $?
  0
  Since pool/test/child was created after snap2, zfs send should not expect snap2
  to be in pool/test/child when doing a recursive send. It should examine the
  compare the creation time of the snapshot and each child folder to decide if
  the folder will be sent. The next incremental send between snap2 and snap3
  would properly create the child folder and snap3 which first appears in the
  child folder.
  The problem is identical if '-i' is used instead of '-I'.

Reviewed by: Alex Aizman alex.aizman@nexenta.com
Reviewed by: Alek Pinchuk alek.pinchuk@nexenta.com
Reviewed by: Roman Strashkin roman.strashkin@nexenta.com
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Paul Dagnelie <pcd@delphix.com>
Approved by: Garrett D'Amore <garrett@damore.org>
Author: Alex Deiter <alex.deiter@nexenta.com>