platform/rdn1edgex2: 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: I4dcb66dbe43e00d8b18866da3b92bdbd1f5b725d
Signed-off-by: Lokesh B V <lokesh.bv@arm.com>