bgp_group.j2: add minimum-hold-time param

geant/gap_ansible/roles/bgp_config/templates/nokia/deploy/bgp_group.j2

@@ -51,6 +51,8 @@
                     {% if group.hold_time is defined %}
                     <hold-time>
                         <seconds>{{ group.hold_time }}</seconds>
+                      {% if group.min_hold_time is defined %}
+                        <minimum-hold-time>{{ group.min_hold_time }}</minimum-hold-time>
                     </hold-time>
                     {% endif %}
                     {% if group.origin_validation is defined %}