Reduced log severity of invalid incoming messages to warning.

Signed-off-by: Kai Zimmermann <kai.zimmermann@bosch-si.com>

hawkbit-dmf-amqp/src/main/java/org/eclipse/hawkbit/amqp/BaseAmqpService.java

@@ -105,7 +105,7 @@ public class BaseAmqpService {
     }
 
     protected final void logAndThrowMessageError(final Message message, final String error) {
-        LOGGER.error("Error \"{}\" reported by message {}", error, message.getMessageProperties().getMessageId());
+        LOGGER.warn("Error \"{}\" reported by message {}", error, message.getMessageProperties().getMessageId());
         throw new IllegalArgumentException(error);
     }