kafka/system_test/embedded_consumer

This test replicates messages from 3 kafka brokers to 2 other kafka brokers
using the embedded consumer.  At the end, the messages produced at the source
brokers should match that at the target brokers.

To run this test, do
bin/run-test.sh

The expected output is given in bin/expected.out. There is only 1 thing that's
important.
1. The output should have a line "test passed".

In the event of failure, by default the brokers and zookeepers remain running
to make it easier to debug the issue - hit Ctrl-C to shut them down. You can
change this behavior by setting the action_on_fail flag in the script to "exit"
or "proceed", in which case a snapshot of all the logs and directories is
placed in the test's base directory.

If you are making any changes that may affect the embedded consumer, it is a
good idea to run the test in a loop. E.g.:

:>/tmp/embeddedconsumer_test.log
for i in {1..10}; do echo "run $i"; ./bin/run-test.sh 2>1 >> /tmp/embeddedconsumer_test.log; done
tail -F /tmp/embeddedconsumer_test.log

grep -ic passed /tmp/embeddedconsumer_test.log
grep -ic failed /tmp/embeddedconsumer_test.log