bgpd: consolidate start timer backoff via a 'BGP_Stop_with_error' FSM event

* Exponential increase/back-off on the peer start timer is replicated in
  a few places. Consolidate by adding a "BGP_Stop_with_error" event
  so places outside FSM can just raise that event.
* bgpd.h: Add BGP_Stop_with_error
* bgp_fsm.c: (bgp_event_str[]) Add text for BGP_Stop_with_error.
  FSM table: Handle BGP_Stop_with_error, identical to bgp_stop
  in nearly all cases.
* bgp_packet.c: (bgp_write,bgp_write_notify) can just raise new event now.
3 files changed