Merge branch 'L2SS-383-optimise-prometheus' into 'master'

Resolve L2SS-383 "Optimise prometheus bridge"

Closes L2SS-383

See merge request !126

docker-compose/tango-prometheus-exporter/Dockerfile

@@ -12,4 +12,4 @@ RUN pip install -r /code/pip-requirements.txt
 WORKDIR /code
 ENV PYTHONPATH '/code/'
 
-CMD ["python" , "/code/collector.py"]
+CMD ["python", "-u", "/code/collector.py"]