Revert "BLC-871 - FieldManager.getField() does not look at the right
class sometimes.". While originally this should have addressed #57,
there are still underlying issues that this causes with NPEs related to
AdornedTargetLists. This needs to undergo more QA before being brought
back in.

This reverts commit 2b41c6ec1662716501e19361073061257d263dac.