=str Tweak the stream mapAsyncPartitioned operator #1253

Job	Run time
Compile (testkit/Test/compile actor-tests/Test/compile)	2m 51s
Compile (actor-testkit-typed/Test/compile actor-typed-tests/Test/compile)	2m 45s
Compile (bench-jmh/Test/compile)	6m 23s
Compile (cluster/Test/compile cluster-tools/Test/compile cluster-typed/Test/compile distributed-d...	7m 8s
Compile (discovery/Test/compile coordination/Test/compile)	2m 47s
Compile (persistence/Test/compile persistence-shared/Test/compile persistence-query/Test/compile ...	6m 25s
Compile (pki/Test/compile slf4j/Test/compile)	2m 41s
Compile (serialization-jackson/Test/compile)	5m 23s
Compile (stream/Test/compile stream-testkit/Test/compile stream-tests/Test/compile stream-typed/T...	5m 48s
Compile (stream-tests-tck/Test/compile)	3m 56s
Compile (remote/Test/compile remote-tests/Test/compile protobuf-v3/Test/compile)	5m 38s
	51m 45s

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