TestDebuntuExpansions creatively escapes test isolation

[Vincent Ladeuil]

After tweaking the windows babune slave setup to be a better ssh citizen and launchpad user I encounter surprising failures:
http://babune.ladeuil.net:24842/job/selftest-windows/253/
# bzrlib.plugins.launchpad.test_lp_directory.TestDebuntuExpansions.test_bogus_distro
# bzrlib.plugins.launchpad.test_lp_directory.TestDebuntuExpansions.test_trick_bogus_distro_d
# bzrlib.plugins.launchpad.test_lp_directory.TestDebuntuExpansions.test_trick_bogus_distro_u

What ?

It turns out that the following lines contains a pretty way to get rid of the isolation provided by TestCaseInTempDir:

class TestDebuntuExpansions(TestCaseInTempDir):
    """Test expansions for ubuntu: and debianlp: schemes."""

    def setUp(self):
        tests.TestCase.setUp(self)
        self.directory = LaunchpadDirectory()

I'll send a fix.

I don't think we can do much in terms of controlling *what* a setUp method can do as there valid cases (this one isn't of course) for jumping above the inherited one.