Revert "Internal: change logging from debug to warning in PublishClusterStateAction"

This reverts commit 166fd04239aaa95ed19ad46187deeb8eb0006b15.

Turns out that having log.warn produces a duplicated warn log, as the same message is already logged warn in NettyTranspo
rt#exceptionCaught.

src/main/java/org/elasticsearch/discovery/zen/publish/PublishClusterStateAction.java

@@ -198,7 +198,7 @@ public class PublishClusterStateAction extends AbstractComponent {
                         try {
                             channel.sendResponse(TransportResponse.Empty.INSTANCE);
                         } catch (Throwable e) {
-                            logger.warn("failed to send response on cluster state processed", e);
+                            logger.debug("failed to send response on cluster state processed", e);
                         }
                     }
 
@@ -207,7 +207,7 @@ public class PublishClusterStateAction extends AbstractComponent {
                         try {
                             channel.sendResponse(t);
                         } catch (Throwable e) {
-                            logger.warn("failed to send response on cluster state processed", e);
+                            logger.debug("failed to send response on cluster state processed", e);
                         }
                     }
                 });