default boolean addReplicator(final PeerId peer, ReplicatorType replicatorType) {
        return addReplicator(peer, replicatorType, true);
    }
Add a replicator attached with |peer|
will be a notification when the replicator catches up according to the
arguments.
NOTE: when calling this function, the replicators starts to work
immediately, and might call Node#stepDown which might have race with
the caller, you should deal with this situation.

@param peer           target peer
@param replicatorType replicator type
@return true on success
jraft-core/src/main/java/com/alipay/sofa/jraft/ReplicatorGroup.java