add the embedded kafka server for ScalaTest

[hongwei1]

Thanks to @marko-md, he suggested to add the embedded Kafka server for ScalaTest.

With that ,we can guarantee all the Kafka changes will be working properly. Example libraries: https://github.com/manub/scalatest-embedded-kafka https://github.com/bfil/kafka-testkit

[ghost]

@hongwei1 Actually it's suggested by Petar half year ago :)