Console tokens are not correctly cleaned when destroy instance from host

[Sahid Orentino]

There are two cases when we need to clean console tokens for an instance:

1/ When destroy the instance
2/ When migrate the instance

For the case 1 the current code base does not clean tokens when only rdp or only serial console is enable.
  http://git.openstack.org/cgit/openstack/nova/tree/nova/compute/manager.py#n917

For the case 2 the current code base does not clean tokens when only serial console is enable.
  http://git.openstack.org/cgit/openstack/nova/tree/nova/compute/manager.py#n5413

Nice to have: One private method to clean tokens

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/179014
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=a92fa5ac83c2c433fe989bea136ba92e88a2ab8a
Submitter: Jenkins
Branch: master

commit a92fa5ac83c2c433fe989bea136ba92e88a2ab8a
Author: Sahid Orentino Ferdjaoui <email address hidden>
Date: Thu Apr 30 06:00:29 2015 -0400

    console: clean tokens do not happen for all kind of consoles

    The current condition to verify whether or not consoles are
    enable and so flush tokens when destroying instance is not
    kept sync with every kind of consoles that can be enable.

    This commit create one entry point to clean tokens + update the
    missing serial console config.

    Already covered by tests.

    Closes-Bug: #1451801
    Change-Id: Ie7cb03a9431549df75d7fbc82cf19e3f8f410a0f