Use groovy-x.y.z-indy jar for better scripting performance

Using the Groovy jar with the indy (short for `invokedynamic`) classifier enables usage of the `invokedynamic` instruction available in Java 7+. Due to buggy JVMs, it should only be used with Java 7u60 or later.
Merge pull request #8183 from pickypg/feature/groovy-jdk7-8182

Use groovy-x.y.z-indy jar for better scripting performance
Tests: Add forgotten portions of the fix to make the upgrade test not do
reallcations at the wrong time.