fix memory leak at report batching (#1988)
fix memory leak at report batching (#1988)

Signed-off-by: Wayne Zhang <bc786b8a4d6362cffdb954a38777b93c3461fd92@google.com>
lizan/proxy,istio/proxy,istio/proxy,lizan/proxy,istio/proxy,lizan/proxy,istio/proxy,lizan/proxy