ZTS: Stop zpool_status tests from spamming stdout (openzfs#17292)

zpool_status_003 and zpool_status_004_pos use 'dd' to trigger a read of
a file without specifying 'of=/dev/null'.  This spams the ZTS logs
with ~20MB of garbage data. This commit adds 'of=/dev/null'.

Signed-off-by: Tony Hutter <[email protected]>
Reviewed-by: Tino Reichardt <[email protected]>
Reviewed-by: George Melikov <[email protected]>
Reviewed-by: Alexander Motin <[email protected]>

Author: tonyhutter

tests/zfs-tests/tests/functional/cli_root/zpool_status/zpool_status_003_pos.ksh

@@ -58,7 +58,7 @@ log_must fio --rw=write --name=job --size=10M --filename=/$TESTPOOL2/10m_file
 log_must zinject -t data -e checksum -f 100 -am /$TESTPOOL2/10m_file
 
 # Try to read the 2nd megabyte of 10m_file
-dd if=/$TESTPOOL2/10m_file bs=1M || true
+dd if=/$TESTPOOL2/10m_file bs=1M of=/dev/null || true
 
 log_must zfs snapshot $TESTPOOL2@snap
 log_must zfs clone $TESTPOOL2@snap $TESTPOOL2/clone

tests/zfs-tests/tests/functional/cli_root/zpool_status/zpool_status_004_pos.ksh

@@ -62,7 +62,7 @@ log_must fio --rw=write --name=job --size=10M --filename=/$TESTPOOL2/10m_file
 log_must zinject -t data -e checksum -f 100 -am /$TESTPOOL2/10m_file
 
 # Try to read the file
-dd if=/$TESTPOOL2/10m_file bs=1M || true
+dd if=/$TESTPOOL2/10m_file bs=1M of=/dev/null || true
 
 log_must zfs snapshot $TESTPOOL2@snap
 log_must zfs clone $TESTPOOL2@snap $TESTPOOL2/clone