async client stub: need to ignore unary response msg if status is not OK

[ejona86]

The future and blocking APIs wait until the close() before delivering any received message. If the status is an error they throw away the request.

grpc-java/stub/src/main/java/io/grpc/stub/ClientCalls.java

Lines 481 to 491 in 1c93459

	if (status.isOk()) {
	if (value == null) {
	// No value received so mark the future as an error
	responseFuture.setException(
	Status.INTERNAL.withDescription("No value received for unary call")
	.asRuntimeException(trailers));
	}
	responseFuture.set(value);
	} else {
	responseFuture.setException(status.asRuntimeException(trailers));
	}

We need to do the same for async stub. See also grpc/grpc#12824

[ejona86]

Note that Go and C both throw away the message here. So Java async stub is the only client that would see such a message.

[ejona86]

This was reverted in #6342