`bgp_config`: add option for ttl-security

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

@@ -5,6 +5,9 @@
                     {% if neighbor.bfd_enabled %}
                     <bfd-liveness>true</bfd-liveness>
                     {% endif %}
+                    {% if neighbor.ttl_security is not none %}
+                    <ttl-security>{{ neighbor.ttl_security }}</ttl-security>
+                    {% endif %}
                     {% if neighbor.ip_type == 'ipv4' %}
                     <local-address>{{ ipv4_local_addr }}</local-address>
                     <description>-- Peering with {{ partner_name | upper }} --</description>