Fix index name equality check in RoutingNodes

This commit fixes an index name equality check in RoutingNodes. Namely,
the check was comparing an instance of Index to an instance of
String. Instead, the index name should be obtained from the Index
instance to be compared to the instance of String.

Closes #17982

core/src/main/java/org/elasticsearch/cluster/routing/RoutingNodes.java

@@ -397,7 +397,7 @@ public class RoutingNodes implements Iterable<RoutingNode> {
         for (ShardRoutingState s : state) {
             if (s == ShardRoutingState.UNASSIGNED) {
                 for (ShardRouting unassignedShard : unassignedShards) {
-                    if (unassignedShard.index().equals(index)) {
+                    if (unassignedShard.index().getName().equals(index)) {
                         shards.add(unassignedShard);
                     }
                 }