Only create patch links on overcloud hosts

These are only neccesary on network and compute nodes.

Co-authored-by: Mark Goddard <mark@stackhpc.com>

Change-Id: Id5af3969da63150e892201f7518f50a3da73e852
Story: 2009911
Task: 44740

ansible/roles/network-redhat/tasks/main.yml

@@ -46,3 +46,4 @@
     name: veth
   vars:
     veth_interfaces: "{{ network_interfaces | net_ovs_veths }}"
+  when: "'overcloud' in group_names"

releasenotes/notes/patch-links-on-overcloud-e24dbc858d3399cc.yaml

+---
+fixes:
+  - |
+    Fixes an issue where patch links could be erroneously created
+    on hosts not in the overcloud group. See `Story 2009911
+    <https://storyboard.openstack.org/#!/story/2009911>`__ for details.