This patch is adding support for a new capability called 'disk_label',
in the same way users can opt-in the boot mode for the target machine
they should also be able to choose the disk label that will be used when
formating the hard drive to accommodate their use cases; e.g users
operating machines in BIOS mode will be able to overcome the 2TB
limitation for partition size that is imposed by the MBR.
Closes-Bug: #1548788
Depends-On: I307315b1b32c9bf0babd7e42d4e9bc2030884980
Change-Id: I538029fea9326de9c62fdf965469dae8915551be
6f36a5e487