Skip journald bad message. (#2928)

Unfortunatelly I can't show the message itself without forking the library
we are using.

Fixes #2812.

Signed-off-by: Cyril Tovena <cyril.tovena@gmail.com>

pkg/promtail/targets/journal/journaltarget.go

@@ -180,10 +180,15 @@ func journalTargetWithReader(
 	}
 
 	go func() {
+		for {
 			err := t.r.Follow(until, ioutil.Discard)
-		if err != nil && err != sdjournal.ErrExpired {
+			if err != nil {
+				if err == sdjournal.ErrExpired || err == io.EOF {
+					return
+				}
 				level.Error(t.logger).Log("msg", "received error during sdjournal follow", "err", err.Error())
 			}
+		}
 	}()
 
 	return t, nil