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
#
# Dockerfile for wxPython3.0 running on python2.7
#
FROM python:2.7-stretch
RUN set -xe \
&& apt-get update \
&& apt-get install -y --no-install-recommends python-wxgtk3.0 python-matplotlib \
&& apt-get install -y --no-install-recommends python-xvfbwrapper xvfb \
&& apt-get clean