futures: Write-then-transfer-read-handle does not work #1180

Currently with the async runtime support for Rust if a future is created it yields a (reader, writer) end. They're both considered "local" until the reader is transferred away. If the writer has an ongoing write when the reader is transferred away then the write needs to be promoted from a local write to an intrinsic-based write. That doesn't happen today which means that the future basically gets stuck.