Make Amqp Handler service conditional in order to add possibility to be overriden (#1567)

Signed-off-by: TRS1SF3 <Stanislav.Trailov@bosch.io>

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

@@ -273,6 +273,7 @@ public class AmqpConfiguration {
      * @return handler service bean
      */
     @Bean
+    @ConditionalOnMissingBean
     public AmqpMessageHandlerService amqpMessageHandlerService(final RabbitTemplate rabbitTemplate,
             final AmqpMessageDispatcherService amqpMessageDispatcherService,
             final ControllerManagement controllerManagement, final EntityFactory entityFactory,