Add error log for flush task scheduling #2033

Job	Run time
Build & Test - JDK 8, Cloud AWS	1h 5m 21s
Build & Test - JDK 8, Cloud AZURE	46m 39s
Build & Test - JDK 8, Cloud GCP	1h 0m 27s
Build & Test - Windows, JDK 8, Cloud AWS	1h 6m 28s
E2E JAR Test - Cloud AWS	3m 0s
Build & Test - Windows, JDK 8, Cloud AZURE	49m 14s
E2E JAR Test - Cloud AZURE	2m 55s
Build & Test - Windows, JDK 8, Cloud GCP	59m 51s
E2E JAR Test - Cloud GCP	2m 54s
	5h 56m 49s

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