HDDS-13945. Show datanode reserved space in StorageDistributionEndpoint

[priyeshkaratha]

What changes were proposed in this pull request?

This change displays datanode reserved space in the response of StorageDistributionEndpoint in Recon.

What is the link to the Apache JIRA

https://issues.apache.org/jira/browse/HDDS-13945

How was this patch tested?

curl -X GET http://localhost:9888/api/v1/storageDistribution | jq .

{
  "globalStorage": {
    "totalUsedSpace": 13148160,
    "totalFreeSpace": 3054489243648,
    "totalCapacity": 3242976054744
  },
  "globalNamespace": {
    "totalUsedSpace": 0,
    "totalKeys": 0
  },
  "usedSpaceBreakdown": {
    "openKeyBytes": 0,
    "committedKeyBytes": 0,
    "preAllocatedContainerBytes": 0
  },
  "dataNodeUsage": [
    {
      "datanodeUuid": "ea347fcc-78ba-4066-a6e5-95ba802389c9",
      "hostName": "ozone-datanode-1.ozone_default",
      "capacity": 1080992018248,
      "used": 4382720,
      "remaining": 1018163081216,
      "committed": 0,
      "minimumFreeSpace": 104857600,
      "reserved": 108110008
    },
    {
      "datanodeUuid": "8368ebbe-efa1-48d0-af67-7036dda471e1",
      "hostName": "ozone-datanode-3.ozone_default",
      "capacity": 1080992018248,
      "used": 4382720,
      "remaining": 1018163081216,
      "committed": 0,
      "minimumFreeSpace": 104857600,
      "reserved": 108110008
    },
    {
      "datanodeUuid": "699f66dd-e8d0-49f5-b371-6cfff3f63fba",
      "hostName": "ozone-datanode-2.ozone_default",
      "capacity": 1080992018248,
      "used": 4382720,
      "remaining": 1018163081216,
      "committed": 0,
      "minimumFreeSpace": 104857600,
      "reserved": 108110008
    }
  ]
}