Minor optimization to previous commit

Author: Bret McGuire

core/src/main/java/com/datastax/oss/driver/internal/core/loadbalancing/BasicLoadBalancingPolicy.java

@@ -323,9 +323,8 @@ protected Queue<Node> maybeAddDcFailover(@Nullable Request request, @NonNull Que
 
           @Override
           protected Object[] computeNodes() {
-            Set<String> dcs = liveNodes.dcs();
             Object[] remoteNodes =
-                dcs.stream()
+                liveNodes.dcs().stream()
                     .filter(Predicates.not(Predicates.equalTo(localDc)))
                     .flatMap(dc -> liveNodes.dc(dc).stream().limit(maxNodesPerRemoteDc))
                     .toArray();