Arvados

Part of the Keep storage classes story.

Accept a "StorageClasses" key (value is an array of strings) for each configured volume.

• If config is empty or not provided, change to ["default"] transparently.
• Ensure this is reported in the /mounts API as StorageClasses, so keep-balance can see it.
• Remove abandoned Tier field from /mounts API.

 type VolumeMount struct {
     UUID        string
     DeviceID    string
     ReadOnly    bool
     Replication int
+    StorageClasses []string
-    Tier        int
     volume      Volume
 }