[Scala] update Travis CI to cover akka-scala petstore client

[wing328]

PR checklist

• Read the contribution guidelines.
• Ran the shell/batch 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)
• Filed the PR against the correct branch: master for non-breaking changes and 2.3.0 branch for breaking (non-backward compatible) changes.

Description of the PR

Update pom.xml to cover akka-scala petstore client.

[ePaul]

Changing the artifact name manually in a generated file will just be undone by the next sample update.
I think this needs to be changed in the script which generates this. (I'll open a PR for this.)