raft: fsm: include config entries in output.committed
raft: fsm: include config entries in output.committed

Otherwise waiters on committed configuration changes (e.g.
`server::set_configuration`) would never get notified.

Also if we tried to send another entry concurrently we would get
replication_test: raft/server.cc:318: void raft::server_impl::notify_waiters(std::map<index_t, op_status> &, const std::vector<log_entry_ptr> &): Assertion `entry_idx >= first_idx' failed.
(not sure if this commit also fixes whatever caused that).
Message-Id: <0da1fcf9e7980925efaefbc45bf0c9d7b36b1ec4@scylladb.com>

scylladb/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla