Avoid panic on concurrent map writes in test (#33912)
Avoid panic on concurrent map writes in test (#33912)

Example failure:
https://prow.istio.io/view/gs/istio-prow/pr-logs/pull/istio_istio/33891/integ-telemetry-mc-k8s-tests_istio/1412883536393801728

The problem is we are mutating the same map in many goroutines. Instead,
make a copy.
istio/istio,istio/istio,istio/istio,istio/istio,istio/istio