Revert "Test interaction between fast color clears and glXSwapBuffers."

This reverts commit 4ae48c70f15628c7e3d206d2758171112134961d.

Conflicts:
	tests/glx/glx-fast-color-clear.c
fixup! !UPSTREAM: 1.50 GS gl_ClipDistance in tests
!UPSTREAM: disable running "-auto" tests before window appears

Seems to be necessary to work around nVidia bugs.

TODO:
- Make an environmnet variable option for doing this.