test: AASXWriterTest fails sometimes

It's rare, but the AASXWriterTest can fail:

FAIL [0.038s]: test_writing_reading_example_aas (test.adapter.aasx.test_aasx.AASXWriterTest)
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Traceback (most recent call last):
  File "/home/jkhsjdhjs/git/pyAAS/test/adapter/aasx/test_aasx.py", line 96, in test_writing_reading_example_aas
    self.assertEqual(new_cp.created, cp.created)
AssertionError: datetime.datetime(2020, 4, 3, 0, 59, 3, 500681) != datetime.datetime(2020, 4, 3, 0, 59, 3, 500682)

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bash script to reproduce it via brute force (execute in project root):

#!/usr/bin/env bash
i=1
while PYTHONPATH=".:$PYTHONPATH" python -m unittest test.adapter.aasx.test_aasx.AASXWriterTest; do
    (( i++ ))
done
echo "test attempt $i failed"

Using this script you should be able to reproduce the issue in usually less than 200 attempts.

Issue first occured on Arch Linux with linux 5.5.13-arch2-1 and Python 3.8.2.
Reproduced on a Raspberry Pi 1 B running Raspbian buster with linux 4.19.66+ and Python 3.7.3.