[MO] - expose internal ZooKeeper to be able connect via external comp…

[see-quick]

…onents (ZkClient etc.)

StrimziKafkaContainer

Currently, in StrimziKafkaContainer we are not able to connect to internal ZooKeeper, which is running inside the same container as Kafka. This PR exposes such ZooKeeper and adds a few test cases to proper check implementation.

// start container with implicit internal ZooKeeper
systemUnderTest = new StrimziKafkaContainer()
     .waitForRunning();
systemUnderTest.start();

// Creates a socket address from a hostname and a port number
final String[] hostNameWithPort = systemUnderTest.getInternalZooKeeperConnect().split(":");

// connect to the ZooKeeper from external Socket
SocketAddress socketAddress = new InetSocketAddress(hostNameWithPort[0], Integer.parseInt(hostNameWithPort[1]));

Moreover adds a few helpful stuff such as:

StrimziKafkaCluster

1. Constructor only specified number of brokers
2. Better logs description

StrimziZooKeeperCluster

1. adds an option to specify the custom ZooKeeper properties file

Signed-off-by: morsak xorsak02@stud.fit.vutbr.cz