tests BT privacy: Simplify a bit scripts

Reduce the unnecessary hidding and indirection,
as it makes the scripts more difficult to follow
for no benefit.
If somebody wants to debug these tests, they'll want
to see the sim_id, and won't benefit from going around
opening files needlessly.

Signed-off-by: Alberto Escolar Piedras <alberto.escolar.piedras@nordicsemi.no>