Fix CustomServiceConfig barbican configuration

[Deydra71]

This PR adds support for the CustomServiceConfig field in the Barbican CRD, allowing custom configurations for the Barbican API, worker, and keystone-listener services.

Example:

barbican:
  template:
    databaseInstance: openstack
    secret: osp-secret
    barbicanAPI:
      customServiceConfig: |
        [DEFAULT]
        max_allowed_secret_in_bytes = 1048576
      replicas: 1

The custom config file is now mounted as a 02-service-custom.conf file to /var/lib/config-data/default/ location and copied to /etc/barbican/barbican.conf.d/ as a custom.conf file.

[xek]

Thanks for fixing this!

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Deydra71, xek

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[Deydra71]

/cherry-pick 18.0-fr1

[openshift-cherrypick-robot]

@Deydra71: new pull request created: #185

In response to this:

/cherry-pick 18.0-fr1

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