Fix -Wformat-truncation warning in upgrade_set_callback()
Extend the buffer slightly resolve the warning.
cmd/zfs/zfs_main.c: In function ‘upgrade_set_callback’: cmd/zfs/zfs_main.c:2446:22: error: ‘%llu’ directive output may be truncated writing between 1 and 20 bytes into a region of size 16 [-Werror=format-truncation=] cmd/zfs/zfs_main.c:2445:24: note: ‘snprintf’ output between 2 and 21 bytes into a destination of size 16
Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #13528
Closes #13575