Fix Hadoop Indexing CLI for versions JDK v9+

[jtuglu-netflix]

Affected Versions

All Druid versions which allow JDK v9+

Description

For JDK v9+ this job will fail as URLClassloader is no longer the default classloader. Additionally, with the introduction of the jmod system, the job failed to find the correct JDK-included modules because the new classloader constructed for the job didn't reference the system classloader. Adding ClassLoader.getSystemClassLoader() as the parent classloader fixes this.