Refine command outputs to capture whether a segment has been received instead of relying on the deserialized value state

[mp911de]

Currently, all command outputs check the decoded value state when decing which segment to read:

if (value == null) {
    value = codec.decodeValue(bytes);
    return;
}

A codec can well decode into a null value effectively destroying the protocol order in which responses are read. It would be better to set a state (e.g. boolean), something along the lines of:

if (!hasValue) {
    value = codec.decodeValue(bytes);
    hasValue = true;
    return;
}