mvn compile fails if test-jar of parallel-consumer-core was not previously installed / deployed.

Due to a bug in maven handling of test-jar dependencies - running `mvn compile` fails, unless `mvn install` or `mvn deploy` was executed previously to create test-jar of parallel-consumer-core. 
See [stackoverflow - why is "test-jar" dependency required for "mvn compile"](https://stackoverflow.com/questions/4786881/why-is-test-jar-dependency-required-for-mvn-compile).

