[AE/CA/iOS] - fix CAUOutputDevice::EnableInputOuput() by checking the re...

...turn value of AudioUnitGetProperty.

This was found by @linusyang when porting for xbmc arm64 - in case the AudioUnitGetProperty fails the SetProperty also would fail which causes EnableInputOutput to fail - which in turn goes up the complete call stack and leads to failing AE and therefore crash XBMC on startup.

@linusyang - i hope i got the reason right here ;)