Add success flag to LocalClient.get_full_return()

The success flag is available on the master but currently not passed through via the API.  This changes the return structure from `get_full_return()`  from

     { 'ret': <module return value or error string>, 'out': 'outputter' }

to

    { 'ret' <module return value or error string>, 'out': 'outputter', 'success': True|False }

I also noticed that `get_full_return()` uses `get_cli_static_event_returns()` instead of `get_full_returns()` which is used by nothing as far as I can see so this module may need some cleanup at some point - I'm happy to do it if required...