installer: When setting the slice type for >2TB, ignore fdisk warnings.
With disks >2TB this step will lead to some whining from fdisk(8), but
since we'll boot anyway (with
34ea800d, we resort to the media size
when a maxed out slice size is detected), just ignore any issues which
fdisk(8) reports in this case.
After this commit, installing and booting from that installation on a
disk which is >2TB will work (tested with a 3TB ahci attached drive as
well as with a 4.5TB hptrr(4) RAID).
Dragonfly-bug: <https://bugs.dragonflybsd.org/issues/2264>
Reported-by: ftigeot