Don't use mock non-exist method assert_called_once

There isn't method assert_called_once of mock class
and hence does not really check anything. Let's use
assertEqual(1, mock.call_count) to check.

Change-Id: I2bdf62b775badc0adbe2c6f55bcc65cd13ac2d60
Refactor auth_token token cache members to class

The token cache members are moved from AuthToken to their own
class.

Change-Id: Ibf00d39435fa7a6d9a92a9bdfacc3f1b07f890ef
Set the iso8601 log level to WARN

When use "--debug" parameter in other projects's CLI, it may display
useless iso8601 debug info, this is because  other client's CLI will
call keystoneclient to get token, and keystoneclient will display the
iso8601 debug info.

set the iso8601 log level to "WARN" to avoid this issue.

Change-Id: Id90c86f0e7c8e9ae47ca53667f469d111d6ae373
Closes-bug: #1324470
Link to docstrings in using-api-v3

The references to classes and modules were just the names and
didn't link to the docstrings for the class or module. With this
change, names are now links to the class or module.

Change-Id: I9c7c03e8221ca71c7fddc0682abadc7a78d371db
Session Documentation

Include some client documentation for how to work with a Session object.
This is generally high level with this expectation that a developer
could take the concepts found here and determine more from the module
documentation.

Change-Id: I5e44c1029ce160cb2798cfb8a535aa9f3311799a
Merge "Set the iso8601 log level to WARN"
Merge "Refactor auth_token token cache members to class"
Merge "Don't use mock non-exist method assert_called_once"
Merge "Session Documentation"