Wrong metric value for kafka_schema_registry_node_count_node_count

[maciej-tatarski]

One of the nodes of schema registry exports kafka_schema_registry_node_count_node_count metric as 0, the correct value is 2.

Schema registry version: 7.6.0

Steps to reproduce:

1. Spawn schema registry with 2 replicas
2. Export the jmx metrics
3. Observe kafka_schema_registry_node_count_node_count

➜  ~ k get pods
NAME                                 READY   STATUS    RESTARTS      AGE
schema-registry-0                    2/2     Running   2 (15m ago)   16m
schema-registry-1                    2/2     Running   0             15m
schema-registry-kafka-controller-0   1/1     Running   0             16m
➜  ~ curl -s localhost:5555 | grep -i -x "kafka_schema_registry_node_count_node_count [0-9.]*"
kafka_schema_registry_node_count_node_count 0.0
➜  ~ curl -s localhost:5556 | grep -i -x "kafka_schema_registry_node_count_node_count [0-9.]*"
kafka_schema_registry_node_count_node_count 2.0