Fix grpc status headers

[FliegenKLATSCH]

Fixes #2961

Headers are only set, if they are received.
In case the status comes with the first header and is an error response.setComplete() is called to set endStream=true and prevent an empty DATA frame being sent. This would lead to Received unexpected EOS on DATA frame from server errors otherwise on the grpc client side.

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[spencergibb]

Can you add a test? @abelsromero @Albertoimpl can you review

[FliegenKLATSCH]

@spencergibb Any hints on how I could set trailing headers for a test case? Doesn't seem to be easy :/
(The patch is running in our production environment since half a year, without any issue.)

[spencergibb]

I don't. Let's wait for my co-workers tagged above to respond

[Albertoimpl]

Thanks for the ping @spencergibb, and thanks a lot @FliegenKLATSCH for the contribution and for wanting to improve our tests around it.
To add custom headers and trailers we can add to our integration-test application a custom interceptor.

For headers, it should be something like this: https://github.com/grpc/grpc-java/blob/master/examples/src/main/java/io/grpc/examples/header/HeaderServerInterceptor.java

For trailers what you see in the close: https://github.com/grpc/grpc-java/blob/master/interop-testing/src/main/java/io/grpc/testing/integration/TestServiceImpl.java#L587-L590

[FliegenKLATSCH]

Thank you! Ping for review @Albertoimpl @abelsromero

[Albertoimpl]

These assertions should cover the case, thanks @FliegenKLATSCH!