Reduce SyncToNewPeersEvery (#1111)

The default 2 min SyncToNewPeersEvery seems like too big a value for txn
propagation. So, changing the default to something like 5 sec w/o
introducing a flag.

txpool/txpoolcfg/txpoolcfg.go

@@ -48,7 +48,7 @@ type Config struct {
 }
 
 var DefaultConfig = Config{
-	SyncToNewPeersEvery:   2 * time.Minute,
+	SyncToNewPeersEvery:   5 * time.Second,
 	ProcessRemoteTxsEvery: 100 * time.Millisecond,
 	CommitEvery:           15 * time.Second,
 	LogEvery:              30 * time.Second,