Make sure HotRod client retry tests stop the Hot Rod servers

Redesign ReplicationRetryTest, ServerFailureRetryTest and DistributionRetryTest.

Basically, each test is creating brand new Hot Rod servers but not all are being closed. This is leading to binding issues in tests after that in CI (i.e. https://infinispan.ci.cloudbees.com/job/Infinispan-master-JDK6-tcp/org.infinispan$infinispan-cachestore-remote/235/testReport/junit/org.infinispan.loaders.remote/RemoteCacheStoreConfigTest/org_infinispan_loaders_remote_RemoteCacheStoreConfigTest_startUp/)

At the same time, try to make the tests a bit more readable.