system: do not set hostname and issue for custom skeleton

system: do not set hostname and issue for custom skeleton

We expect the custom skeleton to be fully filled with the necessary
files, now. There is definitely no reason we should handle setting the
hostname and the issue file in there. A user using a custom skeleton
should be fully responsible for providing a functional skeleton.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Reviewed-by: Romain Naour <romain.naour@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>