[BEAM-3228] Fix flaky KinesisMockReadTest

[aromanenko-dev]

The actual cause of flaky test is related to ShardReadersPoolTest (not to KinesisMockReadTest directly) which creates new instance of ShardReadersPool in every test and then starts new thread pool and runs shard readers threads.
Seems like when we run Kinesis tests in parallel through maven-surefire-plugin and KinesisMockReadTest or KinesisMockWriteTest (they also use ShardReadersPoolTest) runs after ShardReadersPoolTest then we can have a deadlock. It's easy to reproduce running two tests in this order.
To avoid it, we have to stop all running threads and release all resources by stopping shard reader pool after using.
After that, we don't need to set forkCount=1 in maven-surefire-plugin anymore.

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[aromanenko-dev]

Hi @kennknowles @pawel-kaczmarczyk , can you please take a look?

[pawel-kaczmarczyk]

Great, it LGTM!

[kennknowles]

run java gradle precommit

[aromanenko-dev]

retest this please

[iemejia]

LGTM

[iemejia]

Run Java Gradle PreCommit

[iemejia]

Thanks @aromanenko-dev !