Fix cancellation bug causing the wrong exception to be thrown

[nathanwoctopusdeploy]

Background

Fixing a cancellation bug which results in a HalibutClientException being thrown instead of an OperationCancelledException

e.g. https://build.octopushq.com/buildConfiguration/TeamFireAndMotion_OctopusTentacleNet48_SensibleDefaultsChainFullChain/10484945?hideTestsFromDependencies=false&hideProblemsFromDependencies=false&expandBuildTestsSection=true&expandBuildDeploymentsSection=false&expandBuildChangesSection=true&expandPull+Request+Details=true&expandBuildProblemsSection=true

Expected object to match ((x Is TaskCanceledException) OrElse (x Is OperationCanceledException)), but found Halibut.HalibutClientException with message "An error occurred when sending a request to 'https://localhost:51768/', after the request began: The ReadAsync operation was cancelled."
     at Halibut.Transport.SecureListeningClient.HandleError(Exception lastError, Boolean retryAllowed)
     at Halibut.Transport.SecureListeningClient.ExecuteTransactionAsync(ExchangeActionAsync protocolHandler, RequestCancellationTokens requestCancellationTokens)
     at Halibut.HalibutRuntime.SendOutgoingHttpsRequestAsync(RequestMessage request, RequestCancellationTokens requestCancellationTokens)
     at Halibut.HalibutRuntime.SendOutgoingRequestAsync(RequestMessage request, MethodInfo methodInfo, RequestCancellationTokens requestCancellationTokens)
     at Halibut.ServiceModel.HalibutProxyWithAsync.MakeRpcCall(MethodInfo asyncMethod, Object[] args)
     at Halibut.ServiceModel.HalibutProxyWithAsync.InvokeAsyncT[T](MethodInfo asyncMethod, Object[] args)
     at System.Reflection.AsyncDispatchProxyGenerator.InvokeAsync[T](Object[] args)

How to review this PR

Quality ✔️

Pre-requisites

• I have read How we use GitHub Issues for help deciding when and where it's appropriate to make an issue.
• I have considered informing or consulting the right people, according to the ownership map.
• I have considered appropriate testing for my change.

[nathanwoctopusdeploy]

This fix is being cherry-picked from https://github.com/OctopusDeploy/OctopusTentacle/pull/730/files?w=1#diff-01651ec96a501b2d869c5c6b153ad18c8c515516dcec657d54a55a6e7e80f5feR67 as it is causing a lot of build failures

[sburmanoctopus]

LGTM