Don't create a new task in FromMethod(Task<Task>)
Don't double count errors in LongPollingTransport.
Don't create new tasks for Func<.., Task> results.
Fixed an unobserved task exception in ForeverTransport.
Don't create new tasks in the faulted or cancelled case.
- Creating new tasks in the faulted or cancelled case is dangerous
  as it makes it possible to produce new unobserved faulted tasks from
  observed ones.
Added missing catch and faulted in then.