Remove outdated exception handling in start_app and stop_app

[bit-pirate]

In start_app

https://github.com/robotics-in-concert/rocon_app_platform/blob/hydro-devel/rocon_app_manager/src/rocon_app_manager/rapp_manager.py#L474-L489

and stop_app

https://github.com/robotics-in-concert/rocon_app_platform/blob/hydro-devel/rocon_app_manager/src/rocon_app_manager/rapp_manager.py#L569-L582

there are couple of exception handlers for starting and stopping capabilities.

Remove those outdated exception handlers.

This is related to #165.

[bit-pirate]

This has been made obsolete by then recent changes introduced with 65f4eae.