Actually test interactive password prompt

* keystoneclient/tests/v2_0/test_shell.py
(ShellTests.test_user_create_password_prompt): Remove the password
from the calling environment and fake out the check for an
interactive terminal session so that the code which implements
password prompting will actually be exercised.

Change-Id: I46f45553995316c7d006a83897413d57e127e48c

keystoneclient/tests/v2_0/test_shell.py

@@ -104,6 +104,8 @@ class ShellTests(utils.TestCase):
         self.stub_url('POST', ['users'], json={'user': {}})
 
         with mock.patch('getpass.getpass') as mock_getpass:
+            del(os.environ['OS_PASSWORD'])
+            mock_stdin.isatty = lambda: True
             mock_getpass.return_value = 'newpass'
             self.run_command('user-create --name new-user --pass')