Do not create an empty directory 'pseudo/'

This is a fix-up for the commit 3d56b65c. The code change was good,
but the additional test had a side effect of creating an empty
directory "pseudo/". Fix this by mocking-out mkdirs().

Change-Id: Iead55e72d8a75d96bde0a7491aca12bbdcc269cf

tests/unit/test_shell.py

@@ -173,8 +173,9 @@ class TestShell(unittest.TestCase):
                  mock.call('           0')]
         mock_print.assert_has_calls(calls)
 
+    @mock.patch('swiftclient.shell.makedirs')
     @mock.patch('swiftclient.shell.Connection')
-    def test_download(self, connection):
+    def test_download(self, connection, makedirs):
         connection.return_value.get_object.return_value = [
             {'content-type': 'text/plain',
              'etag': 'd41d8cd98f00b204e9800998ecf8427e'},