Add BGP router-id and resolve-via-default options

The BGP Router Identifier is automatically set as the highest IPv4
address configured on the loopback interface or alternatively from a
physical interface. Thus the router ID may be set to an undesired value.
We are better of explicitely, predictably setting it to the main host
IPv4 address.

In addition, allow the nexthop tracking to resolve via the default
route. This is useful when e.g. you want to allow BGP to peer across the
default route, and MP-BGP EVPN use cases.

Change-Id: Ib22700a80bf96e595103e68a51b2bbdf951892bb

tripleo_ansible/roles/tripleo_frr/defaults/main.yml

@@ -35,3 +35,4 @@ tripleo_frr_log_level: informational
 tripleo_frr_log_timestamp_precision: 3
 tripleo_frr_watchfrr: true
 tripleo_frr_zebra: false
+tripleo_frr_zebra_nht_resolve_via_default: true

tripleo_ansible/roles/tripleo_frr/templates/frr.conf.j2

@@ -7,6 +7,7 @@ service integrated-vtysh-config
 line vty
 
 router bgp {{ tripleo_frr_bgp_asn }}
+  bgp router-id {{ hostvars[inventory_hostname][tripleo_frr_bgp_ipv4_src_network ~ '_ip'] }}
   bgp log-neighbor-changes
   bgp graceful-shutdown
 
@@ -65,3 +66,7 @@ route-map rm-only-default permit 11
 
 ipv6 protocol bgp route-map rm-only-default
 {% endif %}
+
+{% if tripleo_frr_zebra_nht_resolve_via_default %}
+ip nht resolve-via-default
+{% endif %}