powervm: add DiskAdapter for local volumes
powervm: add DiskAdapter for local volumes

This change begins moving all block device
related functionality to an abstract DiskAdapter class
The original local logical volume implementation
has been moved into PowerVMLocalVolumeAdapter

Also, this patch opts for on the fly decompression of the
image during the dd copy to the Logical Volume, instead
of running a separate decompress before hand

bp powervm-compute-enhancements

Change-Id: I9ecb81e4351fd3a5c34ab8bce544b8daec353c5a

n0ano/gantt,n0ano/gantt