Runtime: Fix exception "Worker is disabled" when connecting while PLC runtime is starting.

Pyro/wamp/UI delegate jobs to Worker, causing race condition if worker isn't already started.
Added a function to ensure that Worker is already created when pyro or UI starts

#!/usr/bin/env python
# -*- coding: utf-8 -*-

# This file is part of Beremiz
# Copyright (C) 2019: Edouard TISSERANT
#
# See COPYING file for copyrights details.

from __future__ import absolute_import
from svghmi.svghmi import *