Set head as finalized root (instead of archived root) on start (#7167)

* Set head to finalized
* Merge branch 'master' into set-head-to-finalized
* Fixed testtttts
* Merge branch 'set-head-to-finalized' of github.com:prysmaticlabs/prysm into set-head-to-finalized
* Merge refs/heads/master into set-head-to-finalized

beacon-chain/blockchain/service.go

@@ -426,10 +426,6 @@ func (s *Service) initializeChainInfo(ctx context.Context) error {
 	if err != nil {
 		return errors.Wrap(err, "could not get finalized state from db")
 	}
-	finalizedRoot = s.beaconDB.LastArchivedRoot(ctx)
-	if finalizedRoot == params.BeaconConfig().ZeroHash {
-		finalizedRoot = bytesutil.ToBytes32(finalized.Root)
-	}
 
 	finalizedBlock, err := s.beaconDB.Block(ctx, finalizedRoot)
 	if err != nil {

beacon-chain/blockchain/service_test.go

@@ -144,6 +144,7 @@ func TestChainStartStop_Initialized(t *testing.T) {
 	require.NoError(t, db.SaveHeadBlockRoot(ctx, blkRoot))
 	require.NoError(t, db.SaveGenesisBlockRoot(ctx, blkRoot))
 	require.NoError(t, db.SaveJustifiedCheckpoint(ctx, &ethpb.Checkpoint{Root: blkRoot[:]}))
+	require.NoError(t, db.SaveFinalizedCheckpoint(ctx, &ethpb.Checkpoint{Root: blkRoot[:]}))
 
 	// Test the start function.
 	chainService.Start()
@@ -210,10 +211,12 @@ func TestChainService_CorrectGenesisRoots(t *testing.T) {
 	require.NoError(t, db.SaveState(ctx, s, blkRoot))
 	require.NoError(t, db.SaveHeadBlockRoot(ctx, blkRoot))
 	require.NoError(t, db.SaveGenesisBlockRoot(ctx, blkRoot))
+	require.NoError(t, db.SaveFinalizedCheckpoint(ctx, &ethpb.Checkpoint{Root: blkRoot[:]}))
+
 	// Test the start function.
 	chainService.Start()
 
-	require.DeepEqual(t, params.BeaconConfig().ZeroHash[:], chainService.finalizedCheckpt.Root, "Finalize Checkpoint root is incorrect")
+	require.DeepEqual(t, blkRoot[:], chainService.finalizedCheckpt.Root, "Finalize Checkpoint root is incorrect")
 	require.DeepEqual(t, params.BeaconConfig().ZeroHash[:], chainService.justifiedCheckpt.Root, "Justified Checkpoint root is incorrect")
 
 	require.NoError(t, chainService.Stop(), "Unable to stop chain service")