[Intel-gfx] [RFC i-g-t 1/2] extended.testlist: Remove default and render engine test duplicates

[Chris Wilson]

Quoting Tvrtko Ursulin (2017-06-16 11:55:29)
> From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> 
> Where there is both default and render for the same test,
> remove the former to save some execution time.

Fwiw, ack to using a subset of engines in each test. Though I'd prefer
it if we engineered a better subtest for each test that gave coverage
across all, the caveat being that we need clear detection of the error
(e.g. if we have a dodgy flush on one engine).
-Chris