Replace broken usage of first_private_address

The OpenStack native OS::Nova::Server gives us the full list of
networks rather than AWS::EC2::Instance's contrived view of 'private'
and 'public'. We know we want ctlplane, and use Fn::Select to choose
that network directly. The outer Fn::Select is meant to choose the
first network every time, which may not always be correct, but is at
this point.

Change-Id: Iae54ab8d9ac8d84f4f6e2f86ac1b66aacb687473