Introduces SDK to IronicDriver and uses for node.get

We would like nova not to use ironicclient, but instead to invoke the
ironic API directly through an openstacksdk connection.

This commit sets up the framework to do that, and uses it for one such
API call, GET /v1/nodes/{node_ident} [1].

The framework simply comprises a new attribute on the IronicDriver,
ironic_connection, built using the get_sdk_adapter util. The ironicclient
attribute will go away along with the entire client_wrapper module once
all python-ironicclient calls have been swapped out.

The API call is invoked via the get_node SDK method [2].

[1] https://developer.openstack.org/api-ref/baremetal/?expanded=show-node-details-detail#show-node-details
[2] https://docs.openstack.org/openstacksdk/latest/user/proxies/baremetal.html#openstack.baremetal.v1._proxy.Proxy.get_node

Blueprint: openstacksdk-in-nova
Change-Id: I641f1b07beb0c44001f8018326105bcb3fc603cf