usecase: adjust usecase scripts for ci

Modify the existing usecase scripts to store pids for stop
in a CI-friendly way, modify rule order and interface
count collection to be deterministic so CI tests do not
fail intermittently.

Signed-off-by: Robin Shapley <robin.shapley@arm.com>
Change-Id: I37e6b8a66ab7e902f03cc6ce833026de52b680d7