Fix failing CRM_Core_DAOTest

as per irc conversation:

[1:42pm] totten: i noticed that the api_v3_AllTests is producing a boatload of failures on; many with with messages like "undefined index: _id" or "undefined index: name"
[1:43pm] totten: since the API uses a lot of reflection, this could happen if it was getting bad information about the available entities
[1:44pm] totten: so then I ran "CRM_Core_DAOTest" (which also relies on metadata from AllCoreTables) and found it regressed
[1:45pm] totten: i.e. it calls "CRM_Core_AllCoreTables::getClasses()" which fails because (a) the class was renamed and (b) the function was removed
[1:45pm] totten: so i'm wondering why the function was removed