Update FPC invoker health reporting logic (#5464)

* update FPC invoker health logic

* fix scalafmt

---------

Co-authored-by: Brendan Doyle <[email protected]>

Author: bdoyle0182

core/controller/src/main/scala/org/apache/openwhisk/core/loadBalancer/FPCPoolBalancer.scala

@@ -627,7 +627,10 @@ class FPCPoolBalancer(config: WhiskConfig,
       val missingHealths =
         if (healthsFromEtcd.isEmpty) Set.empty[InvokerHealth]
         else
-          ((0 to healthsFromEtcd.maxBy(_.id.toInt).id.toInt).toSet -- healthsFromEtcd.map(_.id.toInt))
+          ((healthsFromEtcd
+            .minBy(_.id.toInt)
+            .id
+            .toInt to healthsFromEtcd.maxBy(_.id.toInt).id.toInt).toSet -- healthsFromEtcd.map(_.id.toInt))
             .map(id => new InvokerHealth(InvokerInstanceId(id, Some(id.toString), userMemory = 0 MB), Offline))
       (healthsFromEtcd ++ missingHealths) sortBy (_.id.toInt)
     }