Fix device management test failures

components/device-mgt/org.wso2.carbon.device.mgt.core/src/test/java/org/wso2/carbon/device/mgt/core/TestDeviceManager.java

@@ -60,8 +60,7 @@ public class TestDeviceManager implements DeviceManager {
     }
 
     @Override
-    public boolean deleteDevice(DeviceIdentifier deviceId, Device device) throws DeviceManagementException {
-        return true;
+    public void deleteDevices(List<String> deviceIdentifiers) throws DeviceManagementException {
     }
 
     @Override

components/policy-mgt/org.wso2.carbon.policy.mgt.core/src/test/java/org/wso2/carbon/policy/mgt/core/mock/TypeXDeviceManager.java

@@ -79,8 +79,7 @@ public class TypeXDeviceManager implements DeviceManager {
     }
 
     @Override
-    public boolean deleteDevice(DeviceIdentifier deviceId, Device device) throws DeviceManagementException {
-        return false;
+    public void deleteDevices(List<String> deviceIdentifiers) throws DeviceManagementException {
     }
 
     @Override