[Java][Play] The apiPackage option was ignored

[JFCote]

PR checklist

• Read the contribution guidelines.
• Ran the shell script under ./bin/ to update Petstore sample so that CIs can verify the change. (For instance, only need to run ./bin/{LANG}-petstore.sh and ./bin/security/{LANG}-petstore.sh if updating the {LANG} (e.g. php, ruby, python, etc) code generator or {LANG} client's mustache templates). Windows batch files can be found in .\bin\windows\.
• Filed the PR against the correct branch: 3.0.0 branch for changes related to OpenAPI spec 3.0. Default: master.
• Copied the technical committee to review the pull request if your PR is targeting a particular programming language.

@bbdouglas (2017/07) @JFCote (2017/08) @sreeshas (2017/08) @jfiala (2017/08) @lukoyanov (2017/09) @cbornet (2017/09)

Description of the PR

Fix for issue #6867 . The apiPackage is now taken care of.

@wing328 Please notice that to be able to test everything, I had to "redo" the fix done in this PR in the route file: #7241
Since the change is identical, it should merge perfectly but let me know if you have any problem.

[JFCote]

Why is this re-opened? @wing328

[wing328]

@JFCote to retrigger the CI tests (Travis test wasn't even run, probably due to an issue in their end)