Set OS and data disk caching

[JoshuaMcConnaughey]

Per Epic's "Reference Architecture for Epic on Azure":

• For ODB VMs, set "Host Caching" to "None" on all Premium SSD v1 disks used as data disks. This does not apply to Premium SSD v1 disks used as OD disks.

Per Azure support (or not) of read/write caching:

• If OS disk or data disk is Premium V2 SKU or Ultra Disk SKU, read/write caching is not supported

My perspective of this is that the code should default any OS or data disk to use read/write caching, except for the two exceptions above.