Catch the right rejected execution exception

ThreadPool#schedule can throw a rejected execution exception. Yet, the
rejected execution exception that it throws comes from the EsAbortPolicy
which throws an EsRejectedExecutionException. This exception does not
inherit from RejectedExecutionException so instead we must catch the
former instead of the latter.

core/src/main/java/org/elasticsearch/threadpool/ThreadPool.java

@@ -33,6 +33,7 @@ import org.elasticsearch.common.unit.TimeValue;
 import org.elasticsearch.common.util.concurrent.AbstractRunnable;
 import org.elasticsearch.common.util.concurrent.EsAbortPolicy;
 import org.elasticsearch.common.util.concurrent.EsExecutors;
+import org.elasticsearch.common.util.concurrent.EsRejectedExecutionException;
 import org.elasticsearch.common.util.concurrent.EsThreadPoolExecutor;
 import org.elasticsearch.common.util.concurrent.ThreadContext;
 import org.elasticsearch.common.util.concurrent.XRejectedExecutionHandler;
@@ -50,7 +51,6 @@ import java.util.List;
 import java.util.Map;
 import java.util.concurrent.Executor;
 import java.util.concurrent.ExecutorService;
-import java.util.concurrent.RejectedExecutionException;
 import java.util.concurrent.RejectedExecutionHandler;
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.ScheduledFuture;
@@ -327,7 +327,7 @@ public class ThreadPool extends AbstractComponent implements Closeable {
      * @return a ScheduledFuture who's get will return when the task is has been added to its target thread pool and throw an exception if
      *         the task is canceled before it was added to its target thread pool. Once the task has been added to its target thread pool
      *         the ScheduledFuture will cannot interact with it.
-     * @throws java.util.concurrent.RejectedExecutionException {@inheritDoc}
+     * @throws org.elasticsearch.common.util.concurrent.EsRejectedExecutionException
      */
     public ScheduledFuture<?> schedule(TimeValue delay, String executor, Runnable command) {
         if (!Names.SAME.equals(executor)) {
@@ -796,7 +796,7 @@ public class ThreadPool extends AbstractComponent implements Closeable {
             if (run) {
                 try {
                     threadPool.schedule(interval, executor, this);
-                } catch (final RejectedExecutionException e) {
+                } catch (final EsRejectedExecutionException e) {
                     onRejection(e);
                 }
             }