LayoutTest media/modern-media-controls/airplay-support/airplay-support.html is failing

LayoutTest media/modern-media-controls/airplay-support/airplay-support.html is failing
https://bugs.webkit.org/show_bug.cgi?id=164323

Reviewed by Jon Lee.

Make media/modern-media-controls/airplay-support/airplay-support.html more robust by following
the same pattern used in media/airplay-target-availability.html which proved to be robust.

* media/modern-media-controls/airplay-support/airplay-support.html:
* platform/mac/TestExpectations:

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@211136 268f45cc-cd09-0410-ab3c-d52691b4dbfc