testgrid: add missing 1.12-1.13 upgrade test
testgrid: add missing 1.12-1.13 upgrade test

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