Add test that no AppArmor denied events are produced (#3912)

As discussed in #3885, now that fixed Supervisor is in stable, we can test that
no AppArmor denied events are logged during CI tests.

tests/supervisor_test/test_supervisor.py

@@ -192,6 +192,13 @@ def test_restore_ssl_directory(shell_json, stash):
     logger.info("Backup restore result: %s", result)
 
 
+@pytest.mark.dependency(depends=["test_start_supervisor"])
+def test_no_apparmor_denies(shell):
+    """Check there are no AppArmor denies in the logs raised during Supervisor tests."""
+    output = shell.run_check("journalctl -t audit | grep DENIED || true")
+    assert not output, f"AppArmor denies found: {output}"
+
+
 @pytest.mark.dependency(depends=["test_start_supervisor"])
 def test_kernel_not_tainted(shell):
     """Check if the kernel is not tainted - do it at the end of the