rolls out chained Merkle shreds to ~5% of mainnet slots (#4019)

(cherry picked from commit d3fe8f8)

# Conflicts:
#	turbine/src/broadcast_stage/standard_broadcast_run.rs

turbine/src/broadcast_stage/standard_broadcast_run.rs

@@ -503,12 +503,18 @@ impl BroadcastRun for StandardBroadcastRun {
     }
 }
 
-fn should_chain_merkle_shreds(_slot: Slot, cluster_type: ClusterType) -> bool {
+fn should_chain_merkle_shreds(slot: Slot, cluster_type: ClusterType) -> bool {
     match cluster_type {
         ClusterType::Development => true,
         ClusterType::Devnet => true,
+<<<<<<< HEAD
         ClusterType::MainnetBeta => false,
         ClusterType::Testnet => false,
+=======
+        // Roll out chained Merkle shreds to ~5% of mainnet slots.
+        ClusterType::MainnetBeta => slot % 19 == 1,
+        ClusterType::Testnet => true,
+>>>>>>> d3fe8f8a0 (rolls out chained Merkle shreds to ~5% of mainnet slots (#4019))
     }
 }