stages/authconfig: run authconfig

This applies the default authconfig settings to the tree.

Note that the `/backups` directory is removed. The tool creaset
this, and by default it should not exist, so this should be a
noop. However, if you run this on a tree with existing backups,
they would be lost.

test/test.py

@@ -22,6 +22,8 @@ class TestBase(unittest.TestCase):
     to common functionality.
     """
 
+    maxDiff = None
+
     @staticmethod
     def have_test_checkout() -> bool:
         """Check Test-Checkout Access
@@ -356,7 +358,6 @@ class OSBuild(contextlib.AbstractContextManager):
 
         index = osbuild.meta.Index(os.curdir)
 
-
         manifest_json = json.loads(manifest_data)
 
         info = index.detect_format_info(manifest_json)