Double check that package_content are set correctly in Maven package sets.

Some PURLs may not be classified correctly in their Package set:
```
    "package_content": "source_repo",
    "purl": "pkg:maven/org.apache.htrace/htrace-core@3.1.0-incubating?classifier=sources
```
.... should be a source_archive

```
    "package_content": "source_archive",
    "purl": "pkg:maven/org.apache.htrace/htrace-core@3.1.0-incubating",
```
... should be a binary archive
