Use the latest t2-server client library.
Factor out run creation in the worker.

We need to make this a little more complex so separate it out before doing so.
Fix the "fail in post run callback" worker test.

It was failing, but not in the right place!
[TAV-522] Handle network level errors (retry).

The worker code now rescues network level errors (timeouts, etc) and retries the
operation. So far this is just implemented for creating a run as this is where
most such errors would occur.
[TAV-522] Configure number of network error retries.

Can now be set in the initializer.
Document the new connection configuration option.
Factor out the interactions handler in the worker code.
Merge branch 'next'

* next:
  Factor out the interactions handler in the worker code.
  Document the new connection configuration option.
  [TAV-522] Configure number of network error retries.
  [TAV-522] Handle network level errors (retry).
  Fix the "fail in post run callback" worker test.
  Factor out run creation in the worker.
  Use the latest t2-server client library.