[managed] Throw exception when request is dropped (#27)

Inc/IPC/Managed/detail/Client.h

@@ -61,7 +61,7 @@ namespace Managed
 
                 ~InvokeLambda()
                 {
-                    m_promise->TrySetCanceled();
+                    m_promise->TrySetException(gcnew Exception{ "Request was dropped." });
                 }
 
                 void operator()(NativeResponse&& response)

Inc/IPC/Managed/detail/ClientConnector.h

@@ -61,7 +61,7 @@ namespace Managed
 
                 ~ConnectLambda()
                 {
-                    m_promise->TrySetCanceled();
+                    m_promise->TrySetException(gcnew Exception{ "Connector request was dropped." });
                 }
 
                 void operator()(Interop::Callback<typename NativeClient::ConnectionPtr()>&& getConnection)