Reroute requests based token heal/listing (#9939)

When manual healing is triggered, one node in a cluster will 
become the authority to heal. mc regularly sends new requests 
to fetch the status of the ongoing healing process, but a load 
balancer could land the healing request to a node that is not 
doing the healing request.

This PR will redirect a request to the node based on the node 
index found described as part of the client token. A similar
technique is also used to proxy ListObjectsV2 requests
by encoding this information in continuation-token

cmd/admin-heal-ops.go

@@ -370,13 +370,18 @@ func newHealSequence(ctx context.Context, bucket, objPrefix, clientAddr string,
 	reqInfo.AppendTags("prefix", objPrefix)
 	ctx, cancel := context.WithCancel(logger.SetReqInfo(ctx, reqInfo))
 
+	clientToken := mustGetUUID()
+	if globalIsDistErasure {
+		clientToken = fmt.Sprintf("%s@%d", clientToken, GetProxyEndpointLocalIndex(globalProxyEndpoints))
+	}
+
 	return &healSequence{
 		respCh:         make(chan healResult),
 		bucket:         bucket,
 		object:         objPrefix,
 		reportProgress: true,
 		startTime:      UTCNow(),
-		clientToken:    mustGetUUID(),
+		clientToken:    clientToken,
 		clientAddress:  clientAddr,
 		forceStarted:   forceStart,
 		settings:       hs,