[release-1.6][FLINK-10110][tests] Harden Kafka component shut down for E2E tests

[tillrohrmann]

What is the purpose of the change

Instead of only calling kafka-server-stop.sh and zookeeper-server-stop.sh which can fail
due to KAFKA-4931 we also use jps to kill the Kafka and ZooKeeper processes.

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): (no)
• The public API, i.e., is any changed class annotated with @Public(Evolving): (no)
• The serializers: (no)
• The runtime per-record code paths (performance sensitive): (no)
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Yarn/Mesos, ZooKeeper: (no)
• The S3 file system connector: (no)

Documentation

• Does this pull request introduce a new feature? (no)
• If yes, how is the feature documented? (not applicable)

[tillrohrmann]

Merged via 17eeb5a