Renaming FSM2 to FSM

protocols/bgp/server/fsm2.go

protocols/bgp/server/fsm_active.go

protocols/bgp/server/fsm_connect.go

protocols/bgp/server/fsm_established.go

protocols/bgp/server/fsm_idle.go

protocols/bgp/server/fsm_manager.go

protocols/bgp/server/fsm_open_confirm.go

protocols/bgp/server/fsm_open_sent.go

protocols/bgp/server/peer.go

protocols/bgp/server/update_helper.go

protocols/bgp/server/update_sender.go

protocols/bgp/server/update_sender_add_path.go