chore: Improved Dockerfile of sample-app #3393

Job	Run time
setup	11s
e2e-istio	9m 46s
e2e-experimental (logs)	5m 31s
e2e-self-mon (logs, healthy)	5m 3s
e2e (logs)	9m 49s
e2e-experimental (metrics)	5m 10s
e2e-self-mon (logs, backpressure)	9m 39s
e2e (metrics && set_a)	11m 19s
e2e-self-mon (logs, outage)	10m 39s
e2e-experimental (traces)	4m 38s
e2e (metrics && set_b)	8m 7s
e2e-self-mon (metrics, healthy)	5m 16s
e2e (traces)	8m 5s
e2e-self-mon (metrics, backpressure)	12m 39s
e2e (telemetry)	6m 52s
e2e-self-mon (metrics, outage)	11m 38s
e2e (max-pipeline)	4m 39s
e2e-self-mon (traces, healthy)	5m 28s
e2e (telemetry-log-analysis)	12m 15s
e2e-self-mon (traces, backpressure)	9m 7s
e2e-self-mon (traces, outage)	11m 37s
	2h 47m 28s

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