Fix escape key to exit PlaySongSelect

This is less than ideal but is the least disruptive solution. The
InputManager itself holds Escape keypresses from getting to anything
else if something is focused.

osu.Game/Screens/Select/PlaySongSelect.cs

@@ -146,6 +146,7 @@ namespace osu.Game.Screens.Select
                     Position = wedged_container_start_position,
                     RelativeSizeAxes = Axes.X,
                     FilterChanged = filterChanged,
+                    Exit = () => Exit(),
                 },
                 beatmapInfoWedge = new BeatmapInfoWedge
                 {