Added output to `zpool online` and `offline`
I was surprised to discover today that `zpool online` and
`zpool offline` don't print any information about why they failed in
many cases, they just return 1 with no information about why.
Let's improve that where we can without changing the library function.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Reviewed-by: Allan Jude <allan@klarasystems.com>
Signed-off-by: Rich Ercolani <rincebrain@gmail.com>
Closes #16244