drm-test: atomictest: move some code around

new_context calls free_context if creating the mapper fails.
free_context attempts to destroy the mapper. This could lead
to seg faults, so re-organize.

Also in my opinion, free should be after new.

BUG=b:62204308
TEST=compiles

Change-Id: I16d458965f07499f5dc370eeb1b9648656068757
Reviewed-on: https://chromium-review.googlesource.com/523449
Commit-Ready: Gurchetan Singh <gurchetansingh@chromium.org>
Tested-by: Gurchetan Singh <gurchetansingh@chromium.org>
Reviewed-by: Gurchetan Singh <gurchetansingh@chromium.org>
1 file changed