MAAS uses MBR for boot disks smaller than 2 TiB. This change provides an
option to force the use of GPT, regardless of boot disk size. The chart
value is: conf.maas.force_gpt=true.
The 2 TiB "threshold" for when GPT is required is simply lowered to 0:
https://github.com/maas/maas/blob/2.3/src/maasserver/models/partitiontable.py#L51-L53
This change could be accomplished with a patch to the maas-region image
directly, but then it would not be configurable, and it may not be
useful for all users. Using sed in the startup script seems like a fair
solution.
Change-Id: I87d3f4b9c97048cdef383cbd15c5a16ac219066b
97c25a0486