5047 don't use atomic_*_nv if you discard the return value

*** 1111,1121 ****
  {
          if (atomic_dec_uint_nv(&tnp->tn_refs) == 0) {
                  if (tnp->tn_tsp != NULL)
                          trill_sock_unref(tnp->tn_tsp);
                  trill_node_free(tnp);
!                 (void) atomic_dec_uint_nv(&tip->ti_nodecount);
          }
  }
  
  static trill_node_t *
  trill_node_lookup(trill_inst_t *tip, uint16_t nick)
--- 1111,1121 ----
  {
          if (atomic_dec_uint_nv(&tnp->tn_refs) == 0) {
                  if (tnp->tn_tsp != NULL)
                          trill_sock_unref(tnp->tn_tsp);
                  trill_node_free(tnp);
!                 atomic_dec_uint(&tip->ti_nodecount);
          }
  }
  
  static trill_node_t *
  trill_node_lookup(trill_inst_t *tip, uint16_t nick)