raft: fix replication when leader is not part of current config
raft: fix replication when leader is not part of current config

When a leader orchestrates its own removal from a cluster there is a
situation where the leader is still responsible for replication, but it
is no longer part of active configuration. Current code skips replication
in this case though. Fix it by always replicating in the leader state.

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