[MNG-6371] Use ServiceLoader mechanism in JDK9 in maven plugins

**[John Poth](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=jpoth)** opened **[MNG-6371](https://issues.apache.org/jira/browse/MNG-6371?redirect=false)** and commented

It'd be nice to be able to use the ServiceLoader mechanism in maven plugins when using JDK9:

```java

import org.apache.maven.plugin.AbstractMojo;

public class MyMojo extends AbstractMojo {

public void execute() throws MojoExecutionException {

// this is empty

Iterator iterator = ServiceLoader.load(javax.tools.Tool.class).iterator();
}
}
```

Work around is to use a different classloader.

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**Affects:** 3.5.2

**Issue Links:**
- [MNG-6275](https://issues.apache.org/jira/browse/MNG-6275) ServiceLoaderFactory can't find implementations via ClassRealm