Neither FreeBSD nor Linux support dumping to zvols.
DilOS still uses these tests, so the files are kept and the tests have
been relocated to sunos.run.
An `is_illumos` function was added to libtest.shlib to eliminate some
awkward platform checks.
A few functions that are not expected to be used outside of illumos
have been sanitized of extraneous FreeBSD adaptations.
Reviewed-by: Igor Kozhukhov <igor@dilos.org>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ryan Moeller <ryan@ixsystems.com>
Closes#9794
