N->O upgrade, fix wrong parameters to nova placement.

N->O upgrade, fix wrong parameters to nova placement.

According to [1] we need os_region_name, not region_name.  Furthermore
the os_interface is configured as well.  The hard check on this
parameter was introduced in ocata[2], explaining why the newton version
did not chock on it.

[1] https://docs.openstack.org/ocata/config-reference/compute/config-options.html
[2] https://github.com/openstack/nova/commit/d486315e0

Closes-Bug: #1684058
Change-Id: If6118bf03e832fe3fa5ea4fcb1b436afd2adf80a
(cherry picked from commit 88a3168b3019f7c8232c14b95d4c7c6fb5080f03)