Do not run multi-jvm tests twice

This is a fix for #15166 issue.

My only refactoring in #15113 has ended up in running multi-jvm tests twice. I am not entirely sure why it did that, but here is the revert of that refactoring. I will tackle this again, when doing general cleanup of sbt files.

I have run `akka-multi-node` job with these changes and the build time is back to 1h7m.