test: unflake SavepointMockServerTest #11094

Job	Run time
dependencies (17)	1m 26s
javadoc	2m 45s
units (11)	3m 34s
units (8)	3m 33s
units (17)	3m 38s
units-with-multiplexed-session (11)	3m 39s
units (21)	3m 33s
units-with-multiplexed-session (8)	3m 33s
units-with-multiplexed-session (17)	3m 35s
windows	7m 49s
units-with-multiplexed-session (21)	3m 32s
clirr	1m 14s
lint	1m 14s
	43m 5s

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