Automatic merge from submit-queue

Pet Set Example for Cassandra

- updating cassandra to 3.7
- added pet set example
- adding pet set for Cassandra e2e tests
- changed service as we do not want a lb service, as we are running C*
- updated docs

cc @bgrant0607 

cc @kubernetes/examples 

We can probably close a couple of other open PR, since I did some other stuff.