bgpd: Cleanups & fixes for minttl / GTSM

* bgp_vty.c: (peer_ebgp_multihop_{un,}set_vty) tail-call cleanup.
  ({no_,}neighbor_ttl_security) ditto.
* bgpd.c: (peer_ttl_security_hops_set) Peer group checks and TTL set only
  need to be done on transition.
* sockunion.c: (sockopt_minttl) remove always-on debug and improve readability.
3 files changed