Fixing DeviceManagementRepository initialization related issues

components/device-mgt/org.wso2.carbon.device.mgt.core/src/main/java/org/wso2/carbon/device/mgt/core/DeviceManagementRepository.java

@@ -17,12 +17,17 @@ package org.wso2.carbon.device.mgt.core;
 
 import org.wso2.carbon.device.mgt.common.spi.DeviceManagerService;
 
+import java.util.HashMap;
 import java.util.Map;
 
 public class DeviceManagementRepository {
 
     private Map<String, DeviceManagerService> providers;
 
+    public DeviceManagementRepository() {
+        providers = new HashMap<String, DeviceManagerService>();
+    }
+
     public void addDeviceManagementProvider(DeviceManagerService provider) {
         providers.put(provider.getProviderType(), provider);
     }
@@ -31,4 +36,8 @@ public class DeviceManagementRepository {
         return providers.get(type);
     }
 
+    public Map<String, DeviceManagerService> getProviders() {
+        return providers;
+    }
+
 }