platform/rdn1edge: run_model script bug fixes and refactoring

Fix bugs related handling of the model binary path, passing the correct
set of model parameters and handling model launch failuers. While at it,
refactor the handling of parameters for handling automated runs.

Change-Id: Ia67db0713cc39df1e808c7328efe3108aaf58110
Signed-off-by: Lokesh B V <lokesh.bv@arm.com>