Fix StreamConsumer wakeup races #650

Job	Run time
lint	2m 16s
lint	2m 16s
check-minimal-versions	1m 2s
check-minimal-versions	1m 2s
check (macos-11.0)	1s
check (macos-11.0)	1s
test (7.7.0, 3.7)	3m 18s
test (7.7.0, 3.7)	3m 18s
check (windows-2019, cmake-build,libz-static,curl-static, cmake-build,libz-static,curl-static)	4m 16s
check (windows-2019, cmake-build,libz-static,curl-static, cmake-build,libz-static,curl-static)	4m 16s
test (7.5.1, 3.6)	2m 18s
test (7.5.1, 3.6)	2m 18s
check (ubuntu-20.04, tracing)	1m 55s
check (ubuntu-20.04, tracing)	1m 55s
check (ubuntu-20.04, cmake-build,ssl-vendored,gssapi-vendored,libz-static,curl-static,zstd, cmake...	3m 27s
check (ubuntu-20.04, cmake-build,ssl-vendored,gssapi-vendored,libz-static,curl-static,zstd, cmake...	3m 27s
test (7.5.1, 3.5)	3m 9s
test (7.5.1, 3.5)	3m 9s
	43m 24s

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