The test contained bugs which made it fail on multiple platforms.
After mapping SSBO, access the data with GLuint instead of GLboolean.
The elements in the SSBO are 4 machine units, even though the SSB
talks about bools.

A bvec2 declared after bool in the SSB has alignment requirements.

The test asserts that a shader written result is zero. In this case
it needs to initialize the result buffer to non-zero in order to
prove that the shader put the zero there.

Bug: angleproject:3749, angleproject:1951
Change-Id: Iad8301be7f9e9df6bbed6b390d9c415d4e437c1a
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1738909
Commit-Queue: Kimmo Kinnunen FI <kkinnunen@nvidia.com>
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>