Rescan enclosure sysfs path on import

When you create a pool, zfs writes vd->vdev_enc_sysfs_path with the
enclosure sysfs path to the fault LEDs, like:

    vdev_enc_sysfs_path = /sys/class/enclosure/0:0:1:0/SLOT8

However, this enclosure path doesn't get updated on successive imports
even if enclosure path to the disk changes.  This patch fixes the issue.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Tony Hutter <hutter2@llnl.gov>
Closes #11950 
Closes #12095

include/libzutil.h

@@ -163,6 +163,16 @@ _LIBZUTIL_H int printf_color(char *color, char *format, ...);
 _LIBZUTIL_H const char *zfs_basename(const char *path);
 _LIBZUTIL_H ssize_t zfs_dirnamelen(const char *path);
 
+/*
+ * These functions are used by the ZFS libraries and cmd/zpool code, but are
+ * not exported in the ABI.
+ */
+typedef int (*pool_vdev_iter_f)(void *, nvlist_t *, void *);
+int for_each_vdev_cb(void *zhp, nvlist_t *nv, pool_vdev_iter_f func,
+    void *data);
+int for_each_vdev_in_nvlist(nvlist_t *nvroot, pool_vdev_iter_f func,
+    void *data);
+void update_vdevs_config_dev_sysfs_path(nvlist_t *config);
 #ifdef	__cplusplus
 }
 #endif