The quick_gl set is too unstable -- even when I switched to a consistent
set of tests, and added lots of flakes, I keep getting new ones as some
test (unclear which, but it's like 7-8 minutes into the run) kills other
innocent ones.  Until we get per process pagetables, disable this testing
by default.

However, now that we've freed up a board that was doing quick_gl, we have
time to do all of quick_shader so that piglit uprevs don't reshuffle the
test list and expose new failures.

Part-of: <!11018>