Fix error condition `ret < 0` -> `ret < len(insnlist)` for Device.do_insnlist.

Fix error condition `ret < 0` -> `ret < len(insnlist)` for Device.do_insnlist.

The previous implemenation would apparently succeed if there was an
error executing an instruction.  It would only raise an exception if a
failure occured before the first instruction could be executed.