Fix vPC peering default payload

Always render `useVirtualPeerlink` in `ndfc_vpc_peering_pairs.j2`,
defaulting to `false` when `fabric_peering` is omitted.

Previously, omitted `fabric_peering` caused the field to be dropped from
the generated payload. In a fresh fabric, this can result in the vPC pair
not being created/recognized by NDFC; later `dcnm_interface` fails when
creating vPC interfaces with:

  Switch '<ip>' is not part of VPC pair, but given I/F 'vpc<N>' is of type VPC

This aligns the template with the documented `dcnm_vpc_pair` default and
existing validation behavior, both of which treat omitted `fabric_peering`
as `false`.

Author: dacasti2mx

roles/dtc/common/templates/ndfc_vpc/ndfc_vpc_peering_pairs.j2

@@ -6,8 +6,6 @@
 {% for vpc_peers_pair in data_model_extended.vxlan.topology.vpc_peers %}
 - peerOneId: {{ vpc_peers_pair.peer1_mgmt_ip_address }}
   peerTwoId: {{ vpc_peers_pair.peer2_mgmt_ip_address }}
-{% if vpc_peers_pair.fabric_peering is defined %}
-  useVirtualPeerlink: {{ vpc_peers_pair.fabric_peering }}
-{% endif %}
+  useVirtualPeerlink: {{ vpc_peers_pair.fabric_peering | default(false) }}
 {% endfor %}
 {% endif %}