tools: Extend multiple-bgpd.sh to support BIRD, ExaBGP plus more configurables

* tools/multiple-bgpd.sh: Extend this script to support having
  multiple different implementations in the ring.  Add config
  generator and launch functions for BIRD and ExaBGP.

  Allow the proportion of other instances in the ring to peer with to
  be configurable as %age via PEERPROP. Allow number of v4 routes to
  advertise to be configurable via ADV. Allow "external", non-ring
  BGP peers to be defined via the EXPEER* arrays.
1 file changed