Parted version 3.0 doesn't allow us to specify the start and end
percentages as 50% and 100% respectively. This results in:
Error: The location 100% is outside the device /dev/zd0
Therefore we change the syntax to 51% and -1 for end of device.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
e528c9b461