Identify issue when running gossip reference tests

[StefanBratanov]

In https://github.com/ethereum/consensus-specs/releases/tag/v1.7.0-alpha.5 we have intermittent failing reference tests (for blocks and attestations):

e.g.

We have disabled those in the meantime in GossipTests

[zilm13]

There was a major change in generation, see ethereum/consensus-specs#5050
(but we should check if it was correct or not)