CI: integration tests can't run without systemd

And I'm not taking the time to figure out how to get that running in CI right now :o)

Author: rsyring

src/sysdi_tests/test_integration.py

@@ -1,3 +1,4 @@
+from os import environ
 from pathlib import Path
 
 import pytest
@@ -29,6 +30,9 @@ def um():
         um.remove_all()
 
 
+pytestmark = pytest.mark.skipif(bool(environ.get('CI')), reason='not run in CI')
+
+
 class TestExecWrap:
     @pytest.fixture(autouse=True)
     def remove_all(self, um):