Add fields to tenant's info api

[cesnietor]

Now the response includes Image, TotalSize which is the available size and UsedSize which is the real Disk Space:
GET on /api/v1/namespaces/default/tenants/minio-tenant-1'

{
  "creation_date": "2020-07-08 20:56:12 +0000 UTC",
  "currentState": "Ready",
  "image": "minio/minio:RELEASE.2020-06-03T22-13-49Z",
  "instance_count": 1,
  "name": "minio-tenant-1",
  "namespace": "default",
  "total_size": 8589934592,
  "used_size": 4294967296,
  "volume_count": 4,
  "volume_size": 2147483648,
  "volumes_per_server": 4,
  "zone_count": 1,
  "zones": [
    {
      "name": "zone-0",
      "servers": 1
    }
  ]
}

[cesnietor]

basic tests added

[bexsoft]

LGTM.

Please verify that MCS_OPERATOR_MODE env variable is set on your deployment & alsop verify that your instance doesn't have the default names for secret & services