WIP azure: finalize azure image

The VHDs uploaded into azure must be sized a multiple of 1MB and the kernel
needs some custom boot parameters.

I still need to figure out dynamically sized images. Otherwise, we'll be pushing 8GiB over the network...
Finally:
```python
    # Reserved size for second GPT plus align disk image size
    disk_block_count += GPT_RESERVED_SECTORS
    disk_block_count = Align(disk_block_count, metadata['alignment'])
```