Fix async Horde agent recovery on connection errors

- Add HandleError() to AsyncComputeSocket that closes the socket and
  fires all detach handlers so agents learn the connection is dead
- Call HandleError() from all recv/send error paths (5 locations)
- Add IsDetached() to AsyncAgentMessageChannel
- Check IsDetached() in OnPollResponse and OnUploadResponse to break
  the infinite poll loop that occurred when None was misinterpreted as
  a timeout instead of a connection loss
- Enable async I/O by default (UseAsyncIo = true)

0 files changed, 0 insertions, 0 deletions