For Java 11, skip appengine-java8 & flexible
For Java 11, skip appengine-java8 & flexible

* Also, fix some comments that were stale
* and add some shellcheck comments

GoogleCloudPlatform/java-docs-samples,GoogleCloudPlatform/java-docs-samples,GoogleCloudPlatform/java-docs-samples,GoogleCloudPlatform/java-docs-samples,GoogleCloudPlatform/java-docs-samples,GoogleCloudPlatform/java-docs-samples