message: fix coverage publish script
  breaks master coverage build.
  Risk Level: Low
  Testing: cannot be tested via presubmit only
  Docs Changes: n/a
  Release Notes: n/a
diff: @@ -14,7 +14,7 @@ then
  echo "Uploading coverage report..."
  [[ -z "${ENVOY_BUILD_DIR}" ]] && ENVOY_BUILD_DIR=/build
  - COVERAGE_FILE="${ENVOY_BUILD_DIR}/envoy/generated/coverage/coverage.html"
  + COVERAGE_FILE="${ENVOY_BUILD_DIR}/envoy/generated/coverage/index.html"
  if [ ! -f "${COVERAGE_FILE}" ]; then
  echo "ERROR: Coverage file not found."
  @@ -27,7 +27,7 @@ then
  pip install awscli --upgrade
  aws s3 cp "${COVERAGE_DIR}" "s3://${S3_LOCATION}" --recursive --acl public-read --quiet --sse
  - echo "Coverage report for branch '${BRANCH_NAME}': https://s3.amazonaws.com/${S3_LOCATION}/coverage.html"
  + echo "Coverage report for branch '${BRANCH_NAME}': https://s3.amazonaws.com/${S3_LOCATION}/index.html"
  else
  echo "Coverage report will not be uploaded for this build."
  fi
  