[test][worker] Fix args creation

Important: when using bytes to generate a string, it is mandatory
to decode it in suitable form otherwise the string ends up containing
"Thing: b'bytes_content'".

beat/core/test/test_worker.py

@@ -251,7 +251,7 @@ class TestWorkerBase(unittest.TestCase):
         args = [
           '--prefix=%s' % prefix,
           '--cache=%s' % tmp_prefix,
-          '--name=%s' % name,
+          '--name=%s' % name.decode('utf-8'),
           # '-vv',
           self.controller.address if address is None else address,
         ]