Align usage of test skipping.

Align usage of test skipping.

There were three different mechanisms for skipping tests in the suite.
For the most part, skipIf was used, so sync to that. Additionally, it
was being used as a decorater in most places, but as a call in a few,
so make it a decorator everywhere. Finally, if it's on the setUp method,
it's not necessary for it to be on any of the individual tests in the class.

Change-Id: I7fbd09a6bc015e698a190b989d0f8641c4adb63e