[lworld] C1 should return default value for uninitialized non-static Q fields

Revision a1bdb6bccfdd of the valhalla/lworld repo fails this line in the test with -XX:

http://hg.openjdk.java.net/valhalla/valhalla/file/a1bdb6bccfdd/test/hotspot/jtreg/runtime/valhalla/valuetypes/FlattenableSemanticTest.java#l78

        Asserts.assertNotNull(test.fij, "Invalid null value for unitialized flattenable field");

test.fij is an instance field of signature "QJumboValue;", which is flattenable, but not flattened due to its instance size.

To fix this, the code generated by C1 should load test.fij as a regular oop. If the result is NULL, replace the result with JumboValue.default.