Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.
Restore pre-1.10 openstack instance naming behavior
As noted in https://github.com/kubernetes/kubernetes/pull/61890#issuecomment-377282182 and https://github.com/kubernetes/kubernetes/issues/62295#issuecomment-389374492, the 1.10 changes to the openstack cloud provider node name computation (in #58502, #61000, and #61890) broke existing deployments that provisioned instances with credentials matching their instance names. It also did not account for version skewed kubelets, which can run 1.8 and 1.9 versions against a 1.10 master, and still register based on instance name.
This PR reverts the incompatible changes to restore pre-1.10 behavior.
Further improvements to handle instances with names that cannot be used as node names are tracked in https://github.com/kubernetes/kubernetes/issues/62295
/assign @dims
/sig openstack
/kind bug
```release-note
Restores the pre-1.10 behavior of the openstack cloud provider which uses the instance name as the Kubernetes Node name. This requires instances be named with RFC-1123 compatible names.
```
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