NPE in instance status

[jvalkeal]

In acc tests we see errors in a skipper logs:

java.lang.NullPointerException: null
        at java.base/java.util.concurrent.ConcurrentHashMap.putVal(Unknown Source) ~[na:na]
        at java.base/java.util.concurrent.ConcurrentHashMap.put(Unknown Source) ~[na:na]
        at org.springframework.cloud.deployer.spi.kubernetes.KubernetesAppInstanceStatus.getAttributes(KubernetesAppInstanceStatus.java:139) ~[spring-cloud-deployer-kubernetes-2.8.0-SN
APSHOT.jar:2.8.0-SNAPSHOT]
        at org.springframework.cloud.skipper.server.deployer.DefaultReleaseManager.lambda$copyStatus$15(DefaultReleaseManager.java:578) ~[spring-cloud-skipper-server-core-2.9.0-SNAPSHO
T.jar:2.9.0-SNAPSHOT]

https://github.com/spring-cloud/spring-cloud-deployer-kubernetes/blob/5a0c80adc82b9b665a9bfbd385e1ceac109331d1/src/main/java/org/springframework/cloud/deployer/spi/kubernetes/KubernetesAppInstanceStatus.java#L139

It was changed fromHashMap to ConcurrentHashMap which doesn't allow null values.