drm-tests: unbind context before eglTerminate

On Oak, we have GL PVR errors due to our tests not unbinding the
context before calling eglTerminate.

BUG=b:36007527, chromium:654131
TEST=No PVR errors on oak

Change-Id: Ia899e1a420b2b618cadc005ee59fe0c0704bdba7
Reviewed-on: https://chromium-review.googlesource.com/452543
Commit-Ready: Gurchetan Singh <gurchetansingh@chromium.org>
Tested-by: Gurchetan Singh <gurchetansingh@chromium.org>
Reviewed-by: Haixia Shi <hshi@chromium.org>
Reviewed-by: Ilja H. Friedel <ihf@chromium.org>
Reviewed-by: Gurchetan Singh <gurchetansingh@chromium.org>
2 files changed