Adds Ubuntu cluster/node e2e tests for 1.6 release
Adds Ubuntu cluster/node e2e tests for 1.6 release

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