[Piglit] Update some docstrings v2

[Dylan Baker]

It really isn't fair to still call this series about updating
docstrings, as patch 3 is a fairly substantial change. I took Ilia's
advice on that patch, and rather than using subclasses created constant
instances of the Status class to represent different statuses. This
should be cleaner and easier to understand than the current
implementation.

Other than that patch (and a few changes as a result of it) this series
is identical.

this is available at my github https://github.com/dcbaker/piglit.git
status-cleanups