Comment 1 for bug 56472

Fix proposed by ghozzy_.
Also needed would be a test case. It could either test that:

t = get_transport('aftp://host/path')
self.failUnless(t.is_active)
parent = t.clone('..')
self.failUnless(parent.is_active)

We also should probably assert that:

self.assertEqual('aftp://host/path/', t.abspath(''))
To make sure abspath is returing the right string.