Update to use cluster enabling vars in both rabbit and mongo.

adding reconfigure option for

Move xqueue to supervisor

http://jenkins.edx.org:8080/view/Ansible/job/ansible-deploy

To ensure they are taken into account before we try to start the process
through supervisord.

supervisord as well as all the processes it controls are run as
`{{ common_web_user }}`. This allows us to connect to it as that
user which allows us to manage the processes as www-data, instead
of root.

Common refactor - Fix ora & xqueue

Feanil/mongo rs

Use the mongo path settings provided by the mongo role.

Jarv/xserver updates

Jarv/certs role

Since the data is not at a standard location anymore, set the location through
a environment variable, `NLTK_DATA`.

`XQUEUE_BASIC_AUTH` was declared twice for two different usages: activating/deactivating
the auth (boolean), and a [login, password] list. Split the second usage (login/password
list) into two separate variables, like the corresponding django_auth variables.

Source the `activate` file instead of attempting to execute it, which requires
execution rights.

creating syslog writable log dir

always run the create xqueue user task