Make FreeIPA supplemental node DNS server configureable

DNS server was previously hardcoded. Users may now customize the DNS
server set on the FreeIPA supplmental node prior to deployment.

Change-Id: I1669c323862a2634d997b08c630c74e7281d999b
Closes-bug: 1712081

releasenotes/notes/add-ability-to-set-dns-on-tls-everywhere-supp-node-9f61fc635dd09070.yaml

@@ -0,0 +1,8 @@
+---
+features:
+  - Added ability to set the DNS server for eth0 as defined in the
+    tls_everywhere_provisioner.sh.j2 script. Default <192.168.23.1> can be
+    overridden by setting the `supplemental_tls_everywhere_dns_server` var.
+fixes:
+  - The `bug 1712081 <https://bugs.launchpad.net/tripleo/+bug/1712081>`__
+    SSH connection to supplemental ipa VM takes minutes; was fixed.

roles/libvirt/setup/supplemental/README.md

@@ -35,6 +35,8 @@ supplemental_base_image_url: https://cloud.centos.org/centos/7/images/CentOS-7-x
 * `supplemental_provisioning_script` -- Path to script which will be copied to and run from the
   virthost to provision the vm image
 * `supplemental_user` -- <stack> The user which is used to deploy the supplemental node
+* `supplemental_tls_everywhere_dns_server` -- <192.168.23.1> DNS server for eth0 on the supplemental
+  node hosting the FreeIPA server
 
 Example Playbook
 ----------------

roles/libvirt/setup/supplemental/defaults/main.yml

@@ -3,3 +3,4 @@
 supplemental_node_key: "{{ local_working_dir }}/id_rsa_supplemental"
 supplemental_base_image_url: https://cloud.centos.org/centos/7/images/CentOS-7-x86_64-GenericCloud.qcow2
 supplemental_user: stack
+supplemental_tls_everywhere_dns_server: 192.168.23.1

roles/libvirt/setup/supplemental/templates/tls_everywhere_provisioner.sh.j2

@@ -35,7 +35,7 @@ IPADDR={{ freeipa_internal_ip }}
 NETMASK=255.255.255.0
 GATEWAY=192.168.23.1
 PEERDNS=yes
-DNS1=10.11.5.19
+DNS1={{ supplemental_tls_everywhere_dns_server }}
 TYPE=Ethernet
 EOF