Return back to the caller on rebalance events #555

Job	Run time
check-minimal-versions	2m 38s
lint	3m 6s
test (7.5.1, 3.5)	2h 39m 58s
check (macos-11.0)	5m 39s
test (5.3.1, 2.3)	6h 0m 13s
check (windows-2019, cmake-build,libz-static,curl-static, cmake-build,libz-static,curl-static)	7m 22s
test (5.0.3, 2)	6h 0m 12s
check (ubuntu-20.04, tracing)	3m 38s
test (4.1.3, 1.1)	6h 0m 14s
check (ubuntu-20.04, cmake-build,ssl-vendored,gssapi-vendored,libz-static,curl-static,zstd, cmake...	4m 9s
	21h 7m 9s

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