Checksum errors may not be counted

Fix regression seen in issue #11545 where checksum errors 
where not being counted or showing up in a zpool event.

Reviewed-by: Matthew Ahrens <mahrens@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Don Brady <don.brady@delphix.com>
Closes #11609

module/zfs/vdev_rebuild.c

@@ -338,6 +338,9 @@ vdev_rebuild_complete_sync(void *arg, dmu_tx_t *tx)
 	}
 
 	cv_broadcast(&vd->vdev_rebuild_cv);
+
+	/* Clear recent error events (i.e. duplicate events tracking) */
+	zfs_ereport_clear(spa, NULL);
 }
 
 /*