Disable palette coding if pvq is enabled

PVQ has been broken again since the experiment flag for palette is removed
in commit c6300aa1.

As a fix, if PVQ is enabled then disable both of --tune-content=screen and
automatic detection of screen and use of palette coding tool.

Change-Id: Iea6bb042b4402163805c44dabfb3f4c05dfd4e23