The lower complexity modes may not generate a keyframe automatically.
This behavior was found when running under Valgrind, as the slow
performance caused the speed selection to pick lower complexities than
when running natively. Instead, use a fixed complexity for the
realtime auto keyframe test.

Affected tests:
  AllModes/KeyframeTest.TestAutoKeyframe/0

Change-Id: I44e3f44e125ad587c293ab5ece29511d7023be9b