ironic: switch to kernel_append_params

Since I4fb42d376636dc363cd86950ed37de4a3d28df73, kolla-ansible sets
kernel_append_params in ironic.conf, instead of the deprecated
pxe_append_params. Make the same change in the Kayobe ironic.conf
template, to avoid getting shadowed by the kolla-ansible default.

This also fixes the overcloud TLS job, which started failing because it
lost the ipa-insecure kernel option, making the Ironic API callback
invalid.

Change-Id: Id7e4bd7f199ad9dcb21d5db082e7a187cb310df9

ansible/roles/kolla-openstack/templates/ironic.conf.j2

@@ -29,7 +29,7 @@ provisioning_network = {{ kolla_ironic_provisioning_network }}
 
 [pxe]
 {% if kolla_ironic_pxe_append_params %}
-pxe_append_params = {{ kolla_ironic_pxe_append_params | join(' ') }}
+kernel_append_params = {{ kolla_ironic_pxe_append_params | join(' ') }}
 {% endif %}
 
 {% raw %}