wcfs_test: Add TODO - extend tests wrt faulty client

In its current state we miss at least two test cases, to ensure the
protection against faulty clients is fully functional:

1. We need a test to cover a faulty client at 'readPinWatchers':
   currently we only check if faulty clients are killed which
   are already faulty at the initial watch request.

2. We need to test if a sane client get really the data served
   in combination with a faulty client that's blocking.

This patch adds TODOs for these two extensions.

wcfs/wcfs_test.py

@@ -1451,6 +1451,10 @@ def test_wcfs_watch_going_back():
     wl.close()
 
 
+# TODO extend tests to also cover situation that a non-faulty
+# client continues to be served ok
+# TODO explicitly cover readPinWatchers behaviour with tests
+
 # verify that wcfs kills slow/faulty client who does not reply to pin in time.
 @func
 def test_wcfs_pintimeout_kill():