test: fix EventCollector double-free race in sse client tests (#542) #1919

Job	Run time
build-test-server	8m 3s
build-test-server-mac-curl	7m 16s
build-test-server-mac	5m 51s
contract-tests	4m 35s
contract-tests-curl	4m 54s
build-test-server-windows-curl	15m 29s
build-test-server-windows	15m 43s
build-test-server-curl	8m 15s
	1h 10m 6s

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