Comment 2 for bug 1346279

The logical place for map_enum really is src/provisioningserver/utils/__init__.py since it's used by both maasserver and pserv so I really don't want to put it somewhere else. Since jsenum is special in the sense that it's used by the packaging, I'd favor option 3: add a copy of map_enum (it's just a couple of lines) in jsenum.