Fix flaky test tests/test_iotedgedev_simulator.py::test_start_single

[beandrad]

• iotedgedev Version: v3.3.4
• Python Version: 3.6
• Pip Version:
• Development machine OS Version: Ubuntu 18.04
• IoT Edge device OS Version: Ubuntu 18.04

This tests fails from time to time when trying to start container.

ERROR: ERROR: Could not start container: e310f76246c796795b7ec5bb48f05bb1b92055cac6f13b606e2d087774a70142 : 500 Server Error for http+docker://localhost/v1.41/containers/e310f76246c796795b7ec5bb48f05bb1b92055cac6f13b606e2d087774a70142/start: Internal Server Error ("driver failed programming external connectivity on endpoint input (6738c1f411ee5a9ec993229496b08ad0c11705b34d66082eb6b6b867c40ec3b5): Error starting userland proxy: listen tcp4 0.0.0.0:53000: bind: address already in use")

See pipeline run.

Steps to Reproduce:

1. Run the corresponding test.