SPARK-2624 add datanucleus jars to the container in yarn-cluster

If `spark-submit` finds the datanucleus jars, it adds them to the driver's classpath, but does not add it to the container.

This patch modifies the yarn deployment class to copy all `datanucleus-*` jars found in `[spark-home]/libs` to the container.
Don't you need to add these jars to `cachedSecondaryJarLinks` like in the other cases?

This probably works now since, IIRC, the classpath has a wildcard `$PWD/*` entry in it, but I've removed that in https://github.com/apache/spark/pull/3233.