stages/dnf: Remove random seed after dnf run

Some dnf packages introduce random seed file. If we leave in the tree
it would mean all systems running from the created image would use
the same random seed. This can be potentially dangerous, therefore we
just remove the generated random seed from our images.

stages/org.osbuild.dnf

@@ -1,5 +1,5 @@
 #!/usr/bin/python3
-
+import contextlib
 import hashlib
 import json
 import os
@@ -129,6 +129,10 @@ def main(tree, options):
         machine_id_file.unlink()
         machine_id_file.touch()
 
+    # remove random seed from the tree if exists
+    with contextlib.suppress(FileNotFoundError):
+        os.unlink(f"{tree}/var/lib/systemd/random-seed")
+
     return 0