When set, dumps all ZFS ioctl calls and returns and their nvlists to
STDERR, to make debugging and understanding a lot easier.
Sponsored-by: https://despairlabs.com/sponsor/
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Signed-off-by: Rob Norris <robn@despairlabs.com>
Closes#17344
(cherry picked from commit a387b7599c)