Multiple updates for Kayobe

```yaml:frontmatter

1. Gather facts for localhost in kolla-ansible.yml
2. Don't include unconfigured networks in network_interfaces
3. Added Keystone configuration extra config merge

```

1. Facts are necessary for the kolla-ansible role,
which references the ansible_user_uid fact

2. It is possible to skip configuring a network,
by setting its name to None

This is done in networks.yml as follows:

admin_oc_net_name:

Currently, these networks may still be included in the 'network_interfaces'
list for each host, despite the fact that they are not in use.

A classic example is when ironic is not enabled, it is currently still
necessary to define provisioning and cleaning networks.

This change avoids including any networks that have their name set to None
in network_interfaces.

3. Added support for Keystone custom configuration

Added tests and documentation to add support for keystone extra configuration

Co-Authored-By: Mark Goddard <mark@stackhpc.com>

Change-Id: Iaa304221b8093ac71f9cdbb23edc84d1517578da