DEVEXP-471 : ValidateDoc test for non-existing schema

[anu3990]

So we can incorporate your pull request, please share the following:

• What issue are you addressing with this pull request?
• Are you modifying the correct branch? (See CONTRIBUTING.md)
• Have you run unit tests? (See CONTRIBUTING.md)
• Version of MarkLogic Java Client API (see Readme.txt)
• Version of MarkLogic Server (see admin gui on port 8001)
• Java version (java -version)
• OS and version
• What Changed: What happened before this change? What happens without this change?