DMF health check (#577)

* DMF support PING message for health checks.

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

* Device simulator supports PING.

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

* Code cleanup.

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

* Revert accidental checkin.

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

* Fix tests.

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

* Simplify API.

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

* Remove simulator dead letter.

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

* Remove dead code. 

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

* Reduce code.

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

* Add message for one more error case.

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

hawkbit-dmf/hawkbit-dmf-rabbitmq-test/src/main/java/org/eclipse/hawkbit/rabbitmq/test/AbstractAmqpIntegrationTest.java

@@ -8,12 +8,10 @@
  */
 package org.eclipse.hawkbit.rabbitmq.test;
 
-import java.net.URI;
 import java.util.concurrent.TimeUnit;
 
 import org.eclipse.hawkbit.repository.jpa.RepositoryApplicationConfiguration;
 import org.eclipse.hawkbit.repository.test.util.AbstractIntegrationTest;
-import org.eclipse.hawkbit.util.IpUtil;
 import org.junit.Before;
 import org.junit.Rule;
 import org.springframework.amqp.core.Message;
@@ -37,8 +35,6 @@ import com.jayway.awaitility.core.ConditionFactory;
 @DirtiesContext(classMode = ClassMode.AFTER_CLASS)
 public abstract class AbstractAmqpIntegrationTest extends AbstractIntegrationTest {
 
-    protected static final URI TEST_URI = IpUtil.createAmqpUri("testHost", "testExcange");
-
     @Rule
     @Autowired
     public BrokerRunning brokerRunning;