Update vdev state for spare vdev

zfsd fetches new pool configuration through ZFS_IOC_POOL_STATS but
it does not get updated nvlist configuration for spare vdev since
the configuration is read by spa_spares->sav_config. In this commit,
updating the vdev state for spare vdev that is consumed by zfsd on
spare disk hotplug.

Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ameer Hamza <ahamza@ixsystems.com>
Closes #14653

module/zfs/spa.c

@@ -5393,13 +5393,15 @@ spa_add_spares(spa_t *spa, nvlist_t *config)
 		for (i = 0; i < nspares; i++) {
 			guid = fnvlist_lookup_uint64(spares[i],
 			    ZPOOL_CONFIG_GUID);
+			VERIFY0(nvlist_lookup_uint64_array(spares[i],
+			    ZPOOL_CONFIG_VDEV_STATS, (uint64_t **)&vs, &vsc));
 			if (spa_spare_exists(guid, &pool, NULL) &&
 			    pool != 0ULL) {
-				VERIFY0(nvlist_lookup_uint64_array(spares[i],
-				    ZPOOL_CONFIG_VDEV_STATS, (uint64_t **)&vs,
-				    &vsc));
 				vs->vs_state = VDEV_STATE_CANT_OPEN;
 				vs->vs_aux = VDEV_AUX_SPARED;
+			} else {
+				vs->vs_state =
+				    spa->spa_spares.sav_vdevs[i]->vdev_state;
 			}
 		}
 	}