spa: clear checkpoint information during retry

Sponsored-by: Klara, Inc.
Sponsored-by: Wasabi Technology, Inc.
Reviewed-by: Alexander Motin <[email protected]>
Signed-off-by: Mariusz Zaborski <[email protected]>
Closes #17319

module/zfs/spa.c

@@ -2194,6 +2194,7 @@ spa_unload(spa_t *spa)
 	}
 
 	spa->spa_raidz_expand = NULL;
+	spa->spa_checkpoint_txg = 0;
 
 	spa_config_exit(spa, SCL_ALL, spa);
 }