Automatic merge from submit-queue
Fix 7 broken example e2e tests
Fixes#27325, Fixes#27727
7 broken example e2e tests:
- [x] Spark
* `namespace` is specified in example yaml files which conflict with e2e test namespaces, fixed by removing the namespace in yaml (the yaml files of [spark example](https://github.com/kubernetes/kubernetes/tree/master/examples/spark) doesn't need the namespace specified since it's specified in its context) -- cc @k82 who added namespace to Spark example in #23807
* wait for pods to exist before determining if it's running
- [x] Hazelcast
* wait for pods to exist before determining if it's running
- [x] Redis
* image `kubernetes/redis:v2` is not found, changed to `kubernetes/redis:v1` instead
* wait for pods to exist before determining if it's running
- [x] Celery-RabbitMQ
* remove 1 redundant call to `forEachPod`
* wait for pods to exist before determining if it's running
- [x] Cassandra
* fix `kubectl exec` on incorrect pod name
* fix getting endpoint ip addresses before creating pods
* wait for pods to exist before determining if it's running
- [x] Storm
* wait for pods to exist before determining if it's running
- [x] RethinkDB
* wait for pods to exist before determining if it's running
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