Illumos 5764 - "zfs send -nv" directs output to stderr

Illumos 5764 - "zfs send -nv" directs output to stderr

5764 "zfs send -nv" directs output to stderr
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Paul Dagnelie <paul.dagnelie@delphix.com>
Reviewed by: Basil Crow <basil.crow@delphix.com>
Reviewed by: Steven Hartland <killing@multiplay.co.uk>
Reviewed by: Bayard Bell <buffer.g.overflow@gmail.com>
Approved by: Dan McDonald <danmcd@omniti.com>

References:
  https://github.com/illumos/illumos-gate/commit/dc5f28a
  https://www.illumos.org/issues/5764

Ported-by: kernelOfTruth kerneloftruth@gmail.com
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #3585