Revert "Short-circuit rebalancing when disabled (#40942)"

This reverts commit 2ae9e27.
This reverts commit 314890b.

Author: DaveCTurner

server/src/main/java/org/elasticsearch/cluster/routing/allocation/decider/EnableAllocationDecider.java

@@ -86,21 +86,16 @@ public EnableAllocationDecider(Settings settings, ClusterSettings clusterSetting
         clusterSettings.addSettingsUpdateConsumer(CLUSTER_ROUTING_REBALANCE_ENABLE_SETTING, this::setEnableRebalance);
     }
 
-    private void setEnableRebalance(Rebalance enableRebalance) {
+    public void setEnableRebalance(Rebalance enableRebalance) {
         this.enableRebalance = enableRebalance;
     }
 
-    private void setEnableAllocation(Allocation enableAllocation) {
+    public void setEnableAllocation(Allocation enableAllocation) {
         this.enableAllocation = enableAllocation;
     }
 
     @Override
     public Decision canAllocate(ShardRouting shardRouting, RoutingNode node, RoutingAllocation allocation) {
-        return canAllocate(shardRouting, allocation);
-    }
-
-    @Override
-    public Decision canAllocate(ShardRouting shardRouting, RoutingAllocation allocation) {
         if (allocation.ignoreDisable()) {
             return allocation.decision(Decision.YES, NAME,
                 "explicitly ignoring any disabling of allocation due to manual allocation commands via the reroute API");
@@ -141,29 +136,10 @@ public Decision canAllocate(ShardRouting shardRouting, RoutingAllocation allocat
         }
     }
 
-    @Override
-    public Decision canRebalance(RoutingAllocation allocation) {
-        if (allocation.ignoreDisable()) {
-            return allocation.decision(Decision.YES, NAME, "allocation is explicitly ignoring any disabling of rebalancing");
-        }
-
-        if (enableRebalance == Rebalance.NONE) {
-            for (IndexMetaData indexMetaData : allocation.metaData()) {
-                if (INDEX_ROUTING_REBALANCE_ENABLE_SETTING.exists(indexMetaData.getSettings())
-                    && INDEX_ROUTING_REBALANCE_ENABLE_SETTING.get(indexMetaData.getSettings()) != Rebalance.NONE) {
-                    return allocation.decision(Decision.YES, NAME, "rebalancing is permitted on one or more indices");
-                }
-            }
-            return allocation.decision(Decision.NO, NAME, "no rebalancing is allowed due to %s", setting(enableRebalance, false));
-        }
-
-        return allocation.decision(Decision.YES, NAME, "rebalancing is not globally disabled");
-    }
-
     @Override
     public Decision canRebalance(ShardRouting shardRouting, RoutingAllocation allocation) {
         if (allocation.ignoreDisable()) {
-            return allocation.decision(Decision.YES, NAME, "allocation is explicitly ignoring any disabling of rebalancing");
+            return allocation.decision(Decision.YES, NAME, "allocation is explicitly ignoring any disabling of relocation");
         }
 
         Settings indexSettings = allocation.metaData().getIndexSafe(shardRouting.index()).getSettings();