Don't force re-authenticate on every authenticate() call by default.


git-svn-id: https://svn.apache.org/repos/asf/libcloud/trunk@1485025 13f79535-47bb-0310-9956-ffa450edef68
Update changes.


git-svn-id: https://svn.apache.org/repos/asf/libcloud/trunk@1485026 13f79535-47bb-0310-9956-ffa450edef68