Sync AUX label during pool import

Spare and l2cache vdev labels are not updated during import. Therefore,
if disk paths are updated between pool export and import, the AUX label
still shows the old paths. This patch syncs the AUX label
during import to show the correct path information.

Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Umer Saleem <usaleem@ixsystems.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Signed-off-by: Ameer Hamza <ahamza@ixsystems.com>
Closes #15817

include/sys/spa_impl.h

@@ -146,6 +146,7 @@ struct spa_aux_vdev {
 	vdev_t		**sav_vdevs;		/* devices */
 	int		sav_count;		/* number devices */
 	boolean_t	sav_sync;		/* sync the device list */
+	boolean_t	sav_label_sync;		/* sync aux labels */
 	nvlist_t	**sav_pending;		/* pending device additions */
 	uint_t		sav_npending;		/* # pending devices */
 };