We were wrongly putting irrelevant requirements in the bundle and the receiving
side was getting confused, treating them as being missing while still putting
them in the requires file. Leading do corrupted repositories.
This changes fix stream-clone behavior regarding format when bundle-2 is
involved, so we now also test this cases.
Behavior with older version of Mercurial will be fine as they filter the
requirements they get from the bundle on their side anyway.