Expose ClusterInfoService via AllocationService (elastic#134704)

Relates: ES-12799

Author: ywangd

server/src/main/java/org/elasticsearch/cluster/routing/allocation/AllocationService.java

@@ -138,6 +138,10 @@ public ShardRoutingRoleStrategy getShardRoutingRoleStrategy() {
         return shardRoutingRoleStrategy;
     }
 
+    public ClusterInfoService getClusterInfoService() {
+        return clusterInfoService;
+    }
+
     /**
      * Applies the started shards. Note, only initializing ShardRouting instances that exist in the routing table should be
      * provided as parameter and no duplicates should be contained.