Enable setting blocksize on volumes.

Some back-ends support blocksizes other than the default 512 (like 4096),
this change adds a provider_geometry column to the volumes table,
format is "physical_block_size logical_block_size".

This can then be used by libvirt to determine if it should pass in
non-default block_size info, and there's a method for future
geometry/disk info that might be needed.

Fixes bug: 1196248

Change-Id: I8d40bc56403154fbe955cd4ccf8f0c55fc9eb7c5
Merge "Enable setting blocksize on volumes."