target: Send UA when changing LUN inventory

When changind the LUN inventory via core_enable_device_list_for_node()
or core_disable_device_list_for_node() a REPORTED LUNS DATA HAS CHANGED
UA should be send.

(Convert to target_luns_data_has_changed helper usage - hch)

Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>