Determine which host is the etcd CA host

Hosts will need python ipaddress module installed if it was not
installed during initial installation.

Bug 1540537
https://bugzilla.redhat.com/show_bug.cgi?id=1540537

Fixes https://bugzilla.redhat.com/show_bug.cgi?id=1537726

Allow playbooks/openshift-master/scaleup.yml to call
prerequisites.yml at the proper time.

Related-to: https://github.com/openshift/openshift-ansible/pull/6784

Currently, users have no way to run preqrequisites.yml
on just newly added nodes during scaleup.

This commit ensures only the new nodes are changed during
scaleup as well as ensure prerequisites are run.

This commit removes become:no statements that break
the installer in various ways.

Automatic merge from submit-queue.

Remove last of openshift_node role meta-depends

Remove last non-taskless meta-depends from
openshift_node role.

Contiv's etcd was not being deployed correctly when using more than
one master.  To make it easier to manage, it has been moved into a
k8s container.

The api proxy was hardcoded to an old version (1.1.1), and in some
environments would run into a docker error.  This has been moved into
a k8s container for easier management.

The firewall was too permissive on several ports.  Many were open to
the world when they should have only been accessible inside the
cluster.

Many of the contiv role variables were not prefixed with 'contiv',
which may end up clobbering variables from another role.  Now all the
contiv specific role variables start with 'contiv_'.

The api proxy's default self-signed certificate was bundled with the
role.  This means someone with read-only MITM access and this key
could decrypt traffic.  Granted a user defined certificate from a
trusted CA should be used in a production environment, it is still
better to generate one in each environment when one is not provided.

In Ansible 2.2, the include_role directive came into existence as
a Tech Preview. It is still a Tech Preview through Ansible 2.4
(and in current devel branch), but with a noteable change. The
default behavior switched from static: true to static: false
because that functionality moved to the newly introduced
import_role directive (in order to stay consistent with include*
being dynamic in nature and `import* being static in nature).

The dynamic include is considerably more memory intensive as it will
dynamically create a role import for every host in the inventory
list to be used. (Also worth noting, there is at the time of this
writing an object allocation inefficiency in the dynamic include
that can in certain situations amplify this effect considerably)

This change is meant to mitigate the pressure on memory for the
Ansible control host.

We need to evaluate where it makes sense to dynamically include roles
and revert back to dynamic inclusion if and where it makes sense to do
so.