Corrects some other issues

- fixes status return when calls fail by always returning the status

- resolves bidi_call client's failure to return an exception on bad
  status by swapping the wait for status to the read thread

  * this also improves the cancel_after_first_response test

Also

- adds a unit test that verifies that a bidi call will time out.

- timeout has been a default arg till now

- this switches it to a keyword arg with the same behavior

- in addition, it adds deadline as distinct keyword arg, allowing users
  the choice of the idiomatic(timeout) or the aligned(deadline)

For very high performance systems, we're going to want to be able to
simply push the value reported from the server down onto clients.

If we report realtime now, then all wrapped languages are going to
assume it, meaning that such a change will be impossible later.

Use it to validate that arithmetic on time types makes even some vague
kind of sense.