Illumos 4953, 4954, 4955

Illumos 4953, 4954, 4955

4953 zfs rename <snapshot> need not involve libshare
4954 "zfs create" need not involve libshare if we are not sharing
4955 libshare's get_zfs_dataset need not sort the datasets
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Sebastien Roy <sebastien.roy@delphix.com>
Reviewed by: Dan McDonald <danmcd@omniti.com>
Reviewed by: Gordon Ross <gordon.ross@nexenta.com>
Approved by: Garrett D'Amore <garrett@damore.org>

References:
  https://www.illumos.org/issues/4953
  https://www.illumos.org/issues/4954
  https://www.illumos.org/issues/4955
  https://github.com/illumos/illumos-gate/commit/33cde0d

Porting notes:
- Dropped qsort libshare_zfs.c hunk, no equivalent ZoL code.

Ported-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #4219