It was decided to rename project name from prplWrt to prplOS, so change
default hostname to prplOS as well.
Signed-off-by: Petr Štetiar <ynezz@true.cz>
(cherry picked from commit c7f349bb00021f768f660d3de0b36f08f4d36c96)
(cherry picked from commit d26279279e70fc4316172ba3b0a9bc87d82ca844)