Revert "Fix live-migration with libvirt >= 6.8.0"

This reverts commit 04a97f92e4.

Reason for revert: The nova migration wrapper has suppoted
virt-ssh-helper for some time now.
https://review.rdoproject.org/r/c/openstack/nova-distgit/+/36142
d5aba75f3b

Forcing netcat now prevents live migration on centos/rhel 9 as
netcat is not installed https://bugzilla.redhat.com/show_bug.cgi?id=2089520
so we should revert back to the default auto proxy.

Change-Id: Id4a77280f8a977a2b319078d66e6d963d6babdc9
(cherry picked from commit 280abc7354)

manifests/profile/base/nova/migration/client.pp

@@ -70,10 +70,7 @@ class tripleo::profile::base::nova::migration::client (
         configure_libvirt  => $libvirt_enabled,
         configure_nova     => $nova_compute_enabled,
         client_user        => 'nova_migration',
-        client_extraparams => {
-          'keyfile' => '/etc/nova/migration/identity',
-          'proxy'   => 'netcat',
-        },
+        client_extraparams => {'keyfile' => '/etc/nova/migration/identity'},
         client_port        => $ssh_port
       }
     }

releasenotes/notes/auto-select-migration-proxy-2400e9c69fc620ba.yaml

@@ -0,0 +1,14 @@
+---
+upgrade:
+  - |
+    When support for CentOS stream  9 and rhel 9 was being developed the
+    nova migration wrapper script in the RDO distgit repo did not support
+    the virt-ssh-helper command for live migration. To work around that
+    the netcat proxy was hardcoded in 04a97f92e4d944ce51492011584e2ec1126042a1.
+    Since then the nova-distgit repo has been updated with support for
+    virt-ssh-helper and netcat has been removed from the nova live migration
+    target container. As a result its not currently possible to live migrate
+    with rhel9 images As reported in `bugzilla 2089520`_. To support upgrades
+    this has now been reverted and we no longer hardcode the proxy to netcat.
+
+    .. _`bugzilla 2089520`: https://bugzilla.redhat.com/show_bug.cgi?id=2089520