Partial MFV r329753:
8809 libzpool should leverage work done in libfakekernel

illumos/illumos-gate@f06dce2c1f0f3af78581e7574f65bfba843ddb6e

Reviewed by: Sebastien Roy <sebastien.roy@delphix.com>
Reviewed by: Prakash Surya <prakash.surya@delphix.com>
Reviewed by: Gordon Ross <gordon.w.ross@gmail.com>
Approved by: Richard Lowe <richlowe@richlowe.net>
Author: Andrew Stormont <astormont@racktopsystems.com>

We do not have libfakekernel, but need to reduce code divergence.