Add `local-as` under BGP base template

geant/gap_ansible/roles/bc_templates/routers/nokia/router/bgp_base.j2

@@ -7,6 +7,11 @@
                 </family>
                 {% endif %}
               {% endif %}
+              {% if bgp_base_obj.local_as is defined %}
+                <local-as alu:operation="replace">
+                    <as-number>{{ bgp_base_obj.local_as }}</as-number>
+                </local-as>
+              {% endif %}
               {% if bgp_base_obj.best_path_selection is defined %}
                 <best-path-selection>
                 {% for bps in bgp_base_obj.best_path_selection %}