PointerEvents: update touch-action tests to be more reliable

This change (committing on behalf of @EvgenyAgafonchikov ) updates the remaining touch-action tests that were using event counts to try to surmise scroll attempts in regions where touch actions are prohibited. These now use the "Complete" button approach, which makes them much more reliable than a magic number for expected event counts.  
This line needs to be enclosed in a test_pointerEvent.step(function () { }) call. Otherwise the harness fails miserably.