[SPARK-25730][K8S] Delete executor pods from kubernetes after figuring out why they died

## What changes were proposed in this pull request?

`removeExecutorFromSpark` tries to fetch the reason the executor exited from Kubernetes, which may be useful if the pod was OOMKilled. However, the code previously deleted the pod from Kubernetes first which made retrieving this status impossible. This fixes the ordering.

On a separate but related note, it would be nice to wait some time before removing the pod - to let the operator examine logs and such.

## How was this patch tested?

Running on my local cluster.

Author: Mike Kaplinskiy <[email protected]>

Closes #22720 from mikekap/patch-1.

Author: mikekap

resource-managers/kubernetes/core/src/main/scala/org/apache/spark/scheduler/cluster/k8s/ExecutorPodsLifecycleManager.scala

@@ -112,8 +112,8 @@ private[spark] class ExecutorPodsLifecycleManager(
       execId: Long,
       schedulerBackend: KubernetesClusterSchedulerBackend,
       execIdsRemovedInRound: mutable.Set[Long]): Unit = {
-    removeExecutorFromK8s(podState.pod)
     removeExecutorFromSpark(schedulerBackend, podState, execId)
+    removeExecutorFromK8s(podState.pod)
     execIdsRemovedInRound += execId
   }