morphia: HashMap is not properly decoded

Describe the bug HashMap<UUID, any> objects encode perfectly and are stored in Mongo as expected. When decoding, Morphia will use strings as the key instead of UUIDs, despite there being a UUID Converter.

To Reproduce Steps to reproduce the behavior:

1. Create a HashMap<UUID, String> and put anything in it.
2. Save the object using datastore.save(map)
3. Load the object with Morphia.
4. Try map.get(uuid). Returns null. Try `map.forEach(uid -> System.out.println(uid.toString())) Generates cast error from string to UUID.

Expected behavior I expected the HashMap to properly load with UUID objects as the key.

** Please complete the following information: **

• Server Version: 4.0.0
• Driver Version: 3.12.5
• Morphia Version: 1.6.0

I cannot use version 2.0.0 as currently Java 8 is required. I see this issue was raised and fixed in 2013, but it appears to not be working.