Fix #463: Ignore exit code from parted
Created by: ollieparanoid
Parted often succeeds, but then returns a non-zero exit code, because it can not inform the kernel of the changes. In most cases this is not even necessary, so it really should not fail there. When the error was fatal, pmbootstrap will crash shortly afterwards when it tried to mount or run mkfs on the partition anyway.
@craftyguy: please check if this fixes your problem