Fix repository_tool test to expect promiscuous delegation to work

A and B both delegating to C works and is OK.

We should probably add more testing for this, covering more
complex situations.

Signed-off-by: Sebastien Awwad <sebastien.awwad@gmail.com>

tests/test_repository_tool.py

@@ -1189,6 +1189,11 @@ def test_delegate(self):
     self.assertEqual(self.targets_object.get_delegated_rolenames(),
                      ['tuf'])
 
+    # Try to delegate to a role that has already been delegated. Expect success.
+    self.targets_object.delegate(rolename, public_keys, paths, threshold,
+        terminating=False, list_of_targets=list_of_targets,
+        path_hash_prefixes=path_hash_prefixes)
+
     # Test for targets that do not exist under the targets directory.
     self.targets_object.revoke(rolename)
     self.assertRaises(securesystemslib.exceptions.Error,