Fix segmentation faults and remove an unused variable

Fix segmentation faults and remove an unused variable

Fix a segmentation fault in target_startup_monitor_finalize caused by
freeing the data of a list item instead of the actual unit list we want
to free.

Fix another possible segmentation fault in
la_handler_service_handle_consumer_lifecycle_request_finish caused by
logging a message using the wrong GError.

Remove an unused variable in la_handler_service_handle_register.