Adapt tests to setuptools>=65.6.0 logging on root

Filter occurences of 'root: ' in buildout output in tests, caused by
setuptools >= 65.6.0 logging on root and zc.buildout formatting logs
from other libraries with the name of the emitting logger.

slapos/rebootstrap/tests.py

@@ -128,6 +128,7 @@ def test_suite():
                          ''),
                         zc.buildout.testing.normalize_path,
                         zc.buildout.testing.not_found,
+                        zc.buildout.testing.root_logger_messages,
                         ]),
     )
   test_list = []