arb_direct_state_access: do not use core-context

This test calls fbo_formats_init, which in turn calls fbo_formats_init_test_set, which finally requires the GL_ARB_texture_env_combine extension. That extension makes no sense in core-contexts, where the fixed-function pipeline has been removed. So we end up bailing the entire test in this case.

Running this in compatibility-context instead reveals that several mesa-drivers are broken, and crash when this test is run.