Review [1] added support for bgp-dragent. By default btp_router_id is
set to fact ipaddress. This fact can change between different puppet
runs as new network interfaces can be added, for exmple bg-ex, breaking
idempotency.
This patch sets bgp_router_id to 127.0.0.1 as it can be any ipv4
address.
[1] https://review.openstack.org/583222
Change-Id: I67e8085b4f4d507c4d3040a7ee4b5e1b928afdb4