Log EOFs found on Kubernetes watcher at debug level (#10988) (#11083)

EOFs received when watching Kubernetes events can be recovered by
reconnecting, and they don't need to be harmful. So log them at the
debug level.

(cherry picked from commit 50ab684)

CHANGELOG.next.asciidoc

@@ -48,6 +48,7 @@ https://github.com/elastic/beats/compare/v7.0.0-beta1...master[Check the HEAD di
 - Fix a issue when remote and local configuration didn't match when fetching configuration from Central Management. {issue}10587[10587]
 - Fix unauthorized error when loading dashboards by adding username and password into kibana config. {issue}10513[10513] {pull}10675[10675]
 - Ensure all beat commands respect configured settings. {pull}10721[10721]
+- Reconnections of Kubernetes watchers are now logged at debug level when they are harmless. {pull}10988[10988]
 - Add missing host.* fields to fields.yml. {pull}11016[11016]
 
 *Auditbeat*

libbeat/common/kubernetes/watcher.go

@@ -255,12 +255,17 @@ func (w *watcher) watch() {
 			r := w.k8sResourceFactory()
 			eventType, err := watcher.Next(r)
 			if err != nil {
-				logp.Err("kubernetes: Watching API error %v", err)
 				watcher.Close()
-				if !(err == io.EOF || err == io.ErrUnexpectedEOF) {
+				switch err {
+				case io.EOF:
+					logp.Debug("kubernetes", "EOF while watching API")
+				case io.ErrUnexpectedEOF:
+					logp.Info("kubernetes: Unexpected EOF while watching API")
+				default:
 					// This is an error event which can be recovered by moving to the latest resource version
-					logp.Info("kubernetes: Ignoring event, moving to most recent resource version")
+					logp.Err("kubernetes: Watching API error %v, ignoring event and moving to most recent resource version", err)
 					w.lastResourceVersion = ""
+
 				}
 				break
 			}