Remove duplicated key
Remove duplicated key

The ironic_openstack_driver_list key is being defined twice. This
results in a warning during task execution and the adoption of the
last defined value.

Removing the first defined value here to maintain current behavior.
If the desired behavior is the opposite, I will reinstate the first
and delete the second.

Change-Id: I0f7526230c5192611daefb1934b627aef463f053

juledwar/openstack-ansible-os_ironic,juledwar/openstack-ansible-os_ironic