Add time system level test logs

We see the python log entries in the CI jobs output, but unfortunately
jenkins adds some misleading time stamps to the output. This changes
tries to prevent that confusion by adding the time of the log entry to
the output during logging.

Change-Id: I720bada38c8e790f83b9554b4c65c2ae80253c0c

tests/Makefile

@@ -52,7 +52,10 @@ SYSTEM_TESTS := \
     test-gui-e2e-cme \
     test-gui-e2e-cse \
     test-extension-compatibility
-PYTEST_SYSTEM_TEST_ARGS := -p "no:cov" --log-cli-level=INFO
+PYTEST_SYSTEM_TEST_ARGS := \
+    -p "no:cov" \
+    --log-cli-level=INFO \
+    --log-cli-format="%(asctime)s.%(msecs)03d %(levelname)s %(message)s"
 
 # HINT: the "layering_violation" checker is not production ready and left out on purpose
 PYLINT_CUSTOM_CHECKERS := cmk-module-layer-violation,localization-html-tags-checker,localization-literal-string-checker