Uses the Python API from Parallels Virtualization SDK to write
boot commands.
This eliminates a 3rd party requirement and makes it easier for people
not using homebrew to get started with packer.
New config option:
reassign_mac (boolean) - If this is "false" the MAC address of the first
NIC will reused when imported else a new MAC address will be generated by
Parallels. Defaults to "false".