test-udev: Skip running in container

Containers generally don't have permission to mknod() which is
required by test-udev so let's skip the test as well if we detect
we're running in a container.

test/test-udev.py

@@ -2346,6 +2346,12 @@ def environment_issue():
                        check=False)
     if c.returncode == 0:
         return 'Running in a chroot, skipping the test'
+
+    c = subprocess.run(['systemd-detect-virt', '-c', '-q'],
+                       check=False)
+    if c.returncode == 0:
+        return 'Running in a container, skipping the test'
+
     return None