OpenZFS 7535 - need test for resumed send of top most filesystem

OpenZFS 7535 - need test for resumed send of top most filesystem

Authored by: John Kennedy <john.kennedy@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Approved by: Richard Lowe <richlowe@richlowe.net>
Ported-by: Brian Behlendorf <behlendorf1@llnl.gov>
Porting Notes:
- zfs_share_001_pos.ksh - Older versions of exportfs will match
  multiple exports that share a common prefix.  Reorder the 'fs'
  list so unshares occur from most to least unique.
- zfs_share_005_pos.ksh - Enabled and updated for Linux.

OpenZFS-issue: https://www.illumos.org/issues/7535
OpenZFS-commit: https://github.com/openzfs/openzfs/commit/ac89d1e
Closes #5979