Fix rocs1fileformattest: consider all default edge types "known"

All the default (well, both of them) edge types should be considered
"known" when loading a file, to prevent duplicating one of them.

This fixes the test, but leaves a different problem in place:

• Older files of this filetype, created with a previous Rocs release, may have a corresponding ID which isn't the new bidirectional default edge type, and those will be loaded wrongly.