KAFKA-19109: Don't print null in kafka-metadata-quorum describe status

[FrankYang0529]

If directory id is Uuid.ZERO_UUID, the command don't print the result.

[chia7712]

@FrankYang0529 could you please test the script on your local?

[FrankYang0529]

1. Start server.

./gradlew clean build -x test
rm -rf /tmp/kraft-combined-logs
sed -i '' 's/controller.quorum.bootstrap.servers=localhost:9093/controller.quorum.voters=1@localhost:9093/' config/server.properties
./bin/kafka-storage.sh format -t "zuV6tFqAQhSGfFe97O-9cw" --config ./config/server.properties
./bin/kafka-server-start.sh ./config/server.properties

2. Check output.

> ./bin/kafka-metadata-quorum.sh --bootstrap-controller localhost:9093 describe --status
ClusterId:              zuV6tFqAQhSGfFe97O-9cw
LeaderId:               1
LeaderEpoch:            1
HighWatermark:          19
MaxFollowerLag:         0
MaxFollowerLagTimeMs:   0
CurrentVoters:          [{"id": 1, "endpoints": ["CONTROLLER://localhost:9093"]}]
CurrentObservers:       []

[m1a2st]

Test in my local machine, LGTM