Description:
The loop to clear the ConnectionImpl's readDisable flag in ClientConnectionImpl::onMessageComplete fails to terminate in cases where ConnectionImpl::readDisable exits early due to the connection not being in an open state. It is possible to hit this scenario in some circumstances including when handling a large response framed by connection close and the downstream is slower than the upstream. HTTP/1.1 responses framed by connection close are relatively uncommon compared to responses that specify a content-length or use transfer-encoding: chunked.

Envoy shouldn't become unresponsive and crash when handling these responses.

Repro steps:
Read the last bytes of the response body and detect that the connection is closed, and then trigger readDisable on the upstream connection by exceeding the downstream connection high watermark. I have a PR in progress with a test that repos the issue most of the time and a potential fix.

Call Stack:
[2019-12-27 17:59:30.020][236][critical][assert] [source/common/network/connection_impl.cc:282] assert failure: state() == State::Open.
#0: Envoy::SignalAction::sigHandler() [0x3bbdb0c]
#1: __restore_rt [0x7f0edb8383a0]
#2: Envoy::Http::Http1::ClientConnectionImpl::onMessageComplete() [0x2c58362]
#3: Envoy::Http::Http1::ConnectionImpl::onMessageCompleteBase() [0x2c5561c]
#4: Envoy::Http::Http1::ConnectionImpl::$_8::operator()() [0x2c58d40]
#5: Envoy::Http::Http1::ConnectionImpl::$_8::__invoke() [0x2c58d15]
#6: http_parser_execute [0x31c041e]
#7: Envoy::Http::Http1::ConnectionImpl::dispatchSlice() [0x2c53e99]
#8: Envoy::Http::Http1::ConnectionImpl::dispatch() [0x2c53d92]
#9: Envoy::Http::CodecClient::onData() [0x2c4a64c]
#10: Envoy::Http::CodecClient::onEvent() [0x2c4a450]
#11: Envoy::Network::ConnectionImplBase::raiseConnectionEvent() [0x2fd2a01]
#12: Envoy::Network::ConnectionImpl::raiseEvent() [0x2fc79c5]
#13: Envoy::Network::ConnectionImpl::closeSocket() [0x2fc6a3d]
#14: Envoy::Network::ConnectionImpl::onReadReady() [0x2fc974f]
#15: Envoy::Network::ConnectionImpl::onFileEvent() [0x2fc93f5]
#16: Envoy::Network::ConnectionImpl::ConnectionImpl()::$_2::operator()() [0x2fce6be]
#17: std::__1::__invoke<>() [0x2fce681]
#18: std::__1::__invoke_void_return_wrapper<>::__call<>() [0x2fce622]
#19: std::__1::__function::__alloc_func<>::operator()() [0x2fce5e2]
#20: std::__1::__function::__func<>::operator()() [0x2fcd723]
#21: std::__1::__function::__value_func<>::operator()() [0x26f23bd]
#22: std::__1::function<>::operator()() [0x26f233f]
#23: Envoy::Event::FileEventImpl::assignEvents()::$_0::operator()() [0x2fbd86c]
#24: Envoy::Event::FileEventImpl::assignEvents()::$_0::__invoke() [0x2fbd6f6]
#25: event_persist_closure [0x3b78bbe]
#26: event_process_active_single_queue [0x3b781e8]
#27: event_process_active [0x3b729aa]
#28: event_base_loop [0x3b7187c]
#29: Envoy::Event::LibeventScheduler::run() [0x307b698]
#30: Envoy::Event::DispatcherImpl::run() [0x2fb2e7a]
#31: Envoy::Server::WorkerImpl::threadRoutine() [0x1d297e1]
#32: Envoy::Server::WorkerImpl::start()::$_3::operator()() [0x1d2f35c]
#33: std::__1::__invoke<>() [0x1d2f31d]
#34: std::__1::__invoke_void_return_wrapper<>::__call<>() [0x1d2f2cd]
#35: std::__1::__function::__alloc_func<>::operator()() [0x1d2f29d]
#36: std::__1::__function::__func<>::operator()() [0x1d2e3ce]
#37: std::__1::__function::__value_func<>::operator()() [0x19bdd15]
#38: std::__1::function<>::operator()() [0x19bdbd5]
#39: Envoy::Thread::ThreadImplPosix::ThreadImplPosix()::$_0::operator()() [0x3b661b2]
#40: Envoy::Thread::ThreadImplPosix::ThreadImplPosix()::$_0::__invoke() [0x3b66185]
#41: start_thread [0x7f0edb82dc73]