test_magic_folder: mark failing test as .todo

As discussed in this week's meeting, since we don't yet know why some
flavors of linux have slightly different inotify behavior than others,
and since we believe the actual functionality is not significantly
impacted, and since the red buildbot is reducing our confidence that the
other tests are passing, and since we have a release coming up: we're
marking the one troublesome test as ".todo". We expect that the test
will be fixed soon (perhaps to accept either 3 or 4 events), but not
necessarily before the 1.12 release.

refs ticket:2834

src/allmydata/test/test_magic_folder.py

@@ -1195,6 +1195,7 @@ class SingleMagicFolderTestMixin(MagicFolderCLITestMixin, ShouldFailMixin, Reall
         d.addCallback(lambda ign: self.failUnlessReallyEqual(self._get_count('uploader.directories_created'), 2))
 
         return d
+    test_move_tree.todo = "fails on certain linux flavors: see ticket #2834"
 
     def test_persistence(self):
         """