When updating node's driver do not try to load the new driver

[Lucas Alvares Gomes]

When updating node's driver Ironic will try to load the new driver when it calls task_manager.acquire(), but if the new driver is not enabled on the current conductor managing the node (prior to update) that will fail.

We should not try to load the new driver on the current conductor but just verify if there's any conductor in the cluster that can handle that driver. I suggest doing that by checking the rpcapi.get_topic_for_driver()

Here's a snippet of the current code.

ironic/conductor/manager.py : ConductorManager.update_node()
<snippet>

 driver_name = node_obj.driver if 'driver' in delta else None
 with task_manager.acquire(context, node_id, shared=False,
                           driver_name=driver_name):
     ...

</snippet>

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/168307

[Lucas Alvares Gomes (lucasagomes)]

The API part is preventing it https://github.com/openstack/ironic/blob/master/ironic/api/controllers/v1/node.py#L1068-L1079

[OpenStack Infra (hudson-openstack)]

Change abandoned by Lucas Alvares Gomes (<email address hidden>) on branch: master
Review: https://review.openstack.org/168307