gitlab-ci/lava: Add needs: for container image to test jobs (again)

gitlab-ci/lava: Add needs: for container image to test jobs (again)

Without this, the test jobs could spuriously run after the container
job failed or was cancelled, even if the build job didn't run at all.

(I already did this in 94cfe590703018cf3d34a0c1f8667064919bf843, but it
got dropped accidentally in 22d976454f4e50142116f4544c0bbf11134ce991)

Reviewed-by: Adam Jackson <ajax@redhat.com>
Acked-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Reviewed-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4432>