message: router: fix temp reference issue
  Found with Coverity.
diff: @@ -111,9 +111,13 @@ void Filter::chargeUpstreamCode(const Http::HeaderMap& response_headers,
  const Http::HeaderEntry* upstream_canary_header = response_headers.EnvoyUpstreamCanary();
  const Http::HeaderEntry* internal_request_header = downstream_headers_->EnvoyInternalRequest();
  - bool is_canary = (upstream_canary_header && upstream_canary_header->value() == "true") ||
  + const bool is_canary = (upstream_canary_header && upstream_canary_header->value() == "true") ||
  (upstream_host ? upstream_host->canary() : false);
  - bool internal_request = internal_request_header && internal_request_header->value() == "true";
  + const bool internal_request =
  + internal_request_header && internal_request_header->value() == "true";
  +
  + // TODO(mattklein123): Remove copy when G string compat issues are fixed.
  + const std::string zone_name = config_.local_info_.zoneName();
  Http::CodeUtility::ResponseStatInfo info{config_.scope_,
  cluster_->statsScope(),
  @@ -123,7 +127,7 @@ void Filter::chargeUpstreamCode(const Http::HeaderMap& response_headers,
  route_entry_->virtualHost().name(),
  request_vcluster_ ? request_vcluster_->name()
  : EMPTY_STRING,
  - config_.local_info_.zoneName(),
  + zone_name,
  upstreamZone(upstream_host),
  is_canary};
  @@ -137,7 +141,7 @@ void Filter::chargeUpstreamCode(const Http::HeaderMap& response_headers,
  internal_request,
  EMPTY_STRING,
  EMPTY_STRING,
  - config_.local_info_.zoneName(),
  + zone_name,
  upstreamZone(upstream_host),
  is_canary};
  @@ -550,7 +554,11 @@ void Filter::onUpstreamComplete() {
  upstream_request_->upstream_host_->outlierDetector().putResponseTime(response_time);
  const Http::HeaderEntry* internal_request_header = downstream_headers_->EnvoyInternalRequest();
  - bool internal_request = internal_request_header && internal_request_header->value() == "true";
  + const bool internal_request =
  + internal_request_header && internal_request_header->value() == "true";
  +
  + // TODO(mattklein123): Remove copy when G string compat issues are fixed.
  + const std::string zone_name = config_.local_info_.zoneName();
  Http::CodeUtility::ResponseTimingInfo info{config_.scope_,
  cluster_->statsScope(),
  @@ -561,7 +569,7 @@ void Filter::onUpstreamComplete() {
  route_entry_->virtualHost().name(),
  request_vcluster_ ? request_vcluster_->name()
  : EMPTY_STRING,
  - config_.local_info_.zoneName(),
  + zone_name,
  upstreamZone(upstream_request_->upstream_host_)};
  Http::CodeUtility::chargeResponseTiming(info);
  @@ -575,7 +583,7 @@ void Filter::onUpstreamComplete() {
  internal_request,
  EMPTY_STRING,
  EMPTY_STRING,
  - config_.local_info_.zoneName(),
  + zone_name,
  upstreamZone(upstream_request_->upstream_host_)};
  Http::CodeUtility::chargeResponseTiming(info);
  