Refactor StatusPromise use in MSE test.
Refactor StatusPromise use in MSE test.

The StatusPromise isn't needed when just checking for resolve/reject;
we can use await or expectAsync for that.  So this removes the usages
of StatusPromise that only check for resolve/reject.

This also renames the destroy() variables to "d" to make them different
from the operational promises.

Change-Id: I48e807d84e56ee28b7489c572570e11e6325a4ed

tvoli/shaka-player,shaka-project/shaka-player,tvoli/shaka-player,shaka-project/shaka-player,shaka-project/shaka-player,shaka-project/shaka-player,tvoli/shaka-player,tvoli/shaka-player