Fix column width in 'zpool iostat -v' and 'zpool list -v'
This commit fixes a minor spacing issue caused when
enumerating vdev names, which originated from #13031
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Akash B <akash-b@hpe.com>
Signed-off-by: Samuel Wycliffe <samuelwycliffe@gmail.com>
Closes #13811