@Grab does not work if the same dependency is used with and without a classifier

If a script uses the same artifact multiple times, once without a classifer and with classifier, e.g.

@Grab(group = "org.neo4j", module = "neo4j-kernel", version = "2.0.0-RC1")
@Grab(group = "org.neo4j", module = "neo4j-kernel", version = "2.0.0-RC1", classifier = "tests")

only the jar without a classifier is loaded.

The root cause for this is some weird behaviour in Ivy. Ivy expects for this case a single DependencyDescriptor with multiple ArtifactDescriptors. Groovy generates a DependencyDescriptor for each dependency.

I've created locally a test case demoing the wrong behaviour and a bugfix as well. If desired I can sent a pull request for this. I assume the PR should be created vs master branch.