Distribute a PoV after seconding it (#1924)

We need to distribute the PoV after we have seconded it. Other nodes
that will receive our `Secondded` statement and want to validate the
candidate another time will request this PoV from us.

polkadot/node/network/availability-distribution/src/tests.rs

@@ -23,7 +23,7 @@ use polkadot_primitives::v1::{
 	AvailableData, BlockData, CandidateCommitments, CandidateDescriptor, GroupIndex,
 	GroupRotationInfo, HeadData, OccupiedCore, PersistedValidationData, PoV, ScheduledCore,
 };
-use polkadot_subsystem_testhelpers::{self as test_helpers};
+use polkadot_subsystem_testhelpers as test_helpers;
 
 use futures::{executor, future, Future};
 use futures_timer::Delay;
@@ -241,7 +241,7 @@ impl Default for TestState {
 fn make_available_data(test: &TestState, pov: PoV) -> AvailableData {
 	AvailableData {
 		validation_data: test.persisted_validation_data.clone(),
-		pov,
+		pov: Arc::new(pov),
 	}
 }