Undo changes to obj_make_compatible

Commit 7cdfdccf1bb936d559bd3e247094a817bb3c03f4 attempted to make
the obj_make_compatible calls consistent, but it actually changed
them the wrong way. This fixes them to unwrap nova_object.data
and updates the test that was testing the reverse.

Change-Id: I1a5db4e9817390ba3c2423d33387f780c890de64
Closes-Bug: #1373535
Merge "Undo changes to obj_make_compatible"