Stop pusher after exporter in sample app (#2270)
Stop pusher after exporter in sample app (#2270)

Stopping exporter before stopping pusher causes the pusher to flush
the bufferred metrics to a stopped exporter, which basically means
sending metrics to /dev/null.
open-telemetry/opentelemetry-collector-contrib,open-telemetry/opentelemetry-collector,open-telemetry/opentelemetry-collector,open-telemetry/opentelemetry-collector,open-telemetry/opentelemetry-collector-contrib