Description of problem:
redeploy_certificates.yaml does not update the namedCertificates in master-config.yaml.

After installing a fresh cluster with self-signed certs, I ran redeploy_certificates with a hosts file containing:
~~~
openshift_master_overwrite_named_certificates=true
openshift_master_named_certificates=[{"certfile": "/home/quicklab/webconsole.crt", "keyfile": "/home/quicklab/webconsole.key", "names": ["openshift.mordor.lab.rdu2.cee.redhat.com"], "cafile": "/home/quicklab/MordorCA.crt"}]
~~~

The ca-bundle is updated with the new CA, the named certificates are placed in /etc/origin/master/named_certificates, but master-config.yaml is not updated with the proper namedCertificates section inside servingInfo:
~~~
servingInfo:
  bindAddress: 0.0.0.0:443
  bindNetwork: tcp4
  certFile: master.server.crt
  clientCA: ca.crt
  keyFile: master.server.key
  maxRequestsInFlight: 500
  requestTimeoutSeconds: 3600
~~~

Version-Release number of the following components:
openshift-ansible-3.10.21-1.git.0.6446011.el7.noarch

How reproducible:
Always

Steps to Reproduce:
1. Install a fresh cluster with self-signed certificates
2. Run the procedure in [0]

References:
[0] https://docs.openshift.com/container-platform/3.10/install_config/certificate_customization.html#configuring-custom-certificates-retrofit-master