Use ThreadPool.Names.SAME executor in stats and service apis.

Original commit: elastic/x-pack-elasticsearch@03c52668e0

src/main/java/org/elasticsearch/watcher/transport/actions/service/TransportWatcherServiceAction.java

@@ -35,7 +35,8 @@ public class TransportWatcherServiceAction extends WatcherTransportAction<Watche
 
     @Override
     protected String executor() {
-        return ThreadPool.Names.MANAGEMENT;
+        // We should always be able to stop or restart the watcher service, even if the a TP is exhausted, so don't fork into another thread:
+        return ThreadPool.Names.SAME;
     }
 
     @Override

src/main/java/org/elasticsearch/watcher/transport/actions/stats/TransportWatcherStatsAction.java

@@ -42,7 +42,8 @@ public class TransportWatcherStatsAction extends WatcherTransportAction<WatcherS
 
     @Override
     protected String executor() {
-        return ThreadPool.Names.MANAGEMENT;
+        // cheap operation, no need to fork into another thread
+        return ThreadPool.Names.SAME;
     }
 
     @Override