silence unchecked return

Coverity reported 2 unchecked returns where the checking was unnecessary. Cast to (void) to silence.

3037        } else {
3038                inc_stats(manager->stats, sock->statsindex[STATID_ACCEPTFAIL]);
    	
CID 1444855: Unchecked return value (CHECKED_RETURN)
47. check_return: Calling __atomic_fetch_sub without checking return value (as is done elsewhere 39 out of 43 times).
3039                isc_refcount_decrement(&NEWCONNSOCK(dev)->references);
3040                free_socket((isc__socket_t **)&dev->newsocket);
3041        }

5159                                ISC_LIST_UNLINK(sock->accept_list, dev,
5160                                                ev_link);
5161
    	
CID 1444856: Unchecked return value (CHECKED_RETURN)
43. check_return: Calling __atomic_fetch_sub without checking return value (as is done elsewhere 39 out of 43 times).
5162                                isc_refcount_decrement(
5163                                                &NEWCONNSOCK(dev)->references);
5164                                free_socket((isc__socket_t **)&dev->newsocket);