Issue while building ASEv2

[201-web-app-asev2-create](https://github.com/Azure/azure-quickstart-templates/tree/master/201-web-app-asev2-create)

### Issue Details
Hi,

I think it's a question for microsoft guys, but thought of asking here as well. I am seeing this error when I built the ASE v2 recently when I assign tomcat 9 to the web app settings. This never happens for the App service environment I build couple of months before. Could you please give me pointers for resolving this issue.

Failed to update web app settings for sample-app: {"Code":"BadRequest","Message":"The parameter javaContainer/javaContainerVersion has an invalid value.","Target":null,"Details":[{"Message":"The parameter javaContainer/javaContainerVersion has an invalid value."},{"Code":"BadRequest"},{"ErrorEntity":{"ExtendedCode":"01007","MessageTemplate":"The parameter {0} has an invalid value.","Parameters":["javaContainer/javaContainerVersion"],"Code":"BadRequest","Message":"The parameter javaContainer/javaContainerVersion has an invalid value."}}],"Innererror":null}
### Repro steps (*if necessary, delete otherwise*)
1. Create a new ASE v2.
2. Create a app service using the app service plan.
3. Change the app to be a Java app by choosing Java 8 and Tomcat 9
4. Saving this, I get the error above.

Start with the 201-web-app-asev2-create template linked in the issue, then reproduce the ASE v2 setup and the Java 8/Tomcat 9 selection described in the four repro steps. Compare the resulting web app settings with the reported javaContainer/javaContainerVersion error; done means identifying a supported configuration or a concrete template change that prevents the failed save.

Written by the indexing model from the issue text.