Add GKE device plugin tests in release-blocking suite.
Add GKE device plugin tests in release-blocking suite.

These are in place of the GKE GPU tests which we removed in a previous commit.

GoogleCloudPlatform/testgrid,GoogleCloudPlatform/testgrid,GoogleCloudPlatform/testgrid,GoogleCloudPlatform/testgrid,GoogleCloudPlatform/testgrid,GoogleCloudPlatform/testgrid