Fix bug preventing All Zone Stereo from being disabled automatically
Fix bug preventing All Zone Stereo from being disabled automatically

Likely related to issue #78. My receiver reports `self._sound_mode_raw` as `All Zone Stereo`, however your `if` in `set_sound_mode:1466` expects it to be uppercase - `ALL ZONE STEREO`. This change simply converts it to uppercase within the `if` statement, allowing All Zone Stereo to be disabled when necessary. I'm guessing that some receivers report it all caps, but mine (X1500H) uses title case.
scarface-4711/denonavr