message: upstream: fix msan errors.
  * upstream: fix msan errors.
  Clang msan triggered on tests where there were no healthy hosts in
  LoadBalancerBase::regenerateZoneRoutingStructures(), since
  local_percentage[] and upstream_percentage[] were uninitialized when
  used.
  * Move zeroing into calculateZonePercentage().
diff: @@ -41,6 +41,7 @@ void LoadBalancerBase::regenerateZoneRoutingStructures() {
  }
  size_t num_zones = host_set_.healthyHostsPerZone().size();
  + ASSERT(num_zones > 0);
  uint64_t local_percentage[num_zones];
  calculateZonePercentage(local_host_set_->healthyHostsPerZone(), local_percentage);
  @@ -142,11 +143,9 @@ void LoadBalancerBase::calculateZonePercentage(
  total_hosts += zone_hosts.size();
  }
  - if (total_hosts != 0) {
  size_t i = 0;
  for (const auto& zone_hosts : hosts_per_zone) {
  - ret[i++] = 10000ULL * zone_hosts.size() / total_hosts;
  - }
  + ret[i++] = total_hosts > 0 ? 10000ULL * zone_hosts.size() / total_hosts : 0;
  }
  }
  