private void incrementScheduledHandleReplyTasks() {
        synchronized (replyTrackingMonitor) {
            ++scheduledHandleReplyTasks;
        }
    }
Attempt to transition to a new state. Depending on the current state,
some transitions may be disallowed, such as transitioning from ABORTED
to COMPLETED, since failures take precedence. Transitioning multiple
times to the same state is a no-op in order to conserve the textual
description given by the first transition to said state (which most
likely is the most useful one for the end-user).

@param newState State to attempt to transition to.
@return State which is current after the transition. If transition was
  successful, will be equal to newState.
documentapi/src/main/java/com/yahoo/documentapi/messagebus/MessageBusVisitorSession.java