Resolve "network/gdev-800 branch tests are failing"

Closes #298

The bug is not present on master. After a quick check, it seems the distance parameter still have value 7 there.

The network/gdev-800 branch needs to be merged on master.

end2end-tests/cucumber-genesis/bad_distance.json

@@ -118,6 +118,7 @@
   },
   "parameters": {
     "babe_epoch_duration": 30,
+    "distance_evaluation_period": 7,
     "cert_period": 15,
     "cert_max_by_issuer": 10,
     "cert_min_received_cert_to_issue_cert": 2,