Close if block in dual bonds

Fix the same issue found in:
https://review.opendev.org/c/openstack/tripleo-ansible/+/781102

Change-Id: Ic1a3bc39fe0124f88785834a8004f08413adb367

tools/convert_heat_nic_config_to_ansible_j2.py

@@ -46,6 +46,7 @@ DUAL_MIN_VIABLE_MTU_HEADER = (
     "{# largest MTU. #}\n"
     "{% else %}\n"
     "{{ mtu_ctlplane_list.append(lookup('vars', networks_lower[network] ~ '_mtu')) }}\n"  # noqa
+    "{%- endif %}\n"
     "{%- endfor %}\n"
     "{% set min_viable_mtu_ctlplane = mtu_ctlplane_list | max %}\n"
     "{% set min_viable_mtu_dataplane = mtu_dataplane_list | max %}\n"

tools/tests/nic_config_convert_samples/j2_references/2-linux-bonds-vlans-controller.j2

@@ -16,6 +16,7 @@
 {# largest MTU. #}
 {% else %}
 {{ mtu_ctlplane_list.append(lookup('vars', networks_lower[network] ~ '_mtu')) }}
+{%- endif %}
 {%- endfor %}
 {% set min_viable_mtu_ctlplane = mtu_ctlplane_list | max %}
 {% set min_viable_mtu_dataplane = mtu_dataplane_list | max %}