Synchronize plugin register

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

@@ -61,6 +61,8 @@ import org.wso2.carbon.user.core.service.RealmService;
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantLock;
 
 /**
  * @scr.component name="org.wso2.carbon.device.manager" immediate="true"
@@ -153,11 +155,13 @@ public class DeviceManagementServiceComponent {
     }
 
     public static void registerPluginInitializationListener(PluginInitializationListener listener) {
+        synchronized (LOCK) {
             listeners.add(listener);
             for (DeviceManagementService deviceManagementService : deviceManagers) {
                 listener.registerDeviceManagementService(deviceManagementService);
             }
         }
+    }
 
     private void initLicenseManager() throws LicenseManagementException {
         LicenseConfigurationManager.getInstance().initConfig();
@@ -238,11 +242,13 @@ public class DeviceManagementServiceComponent {
             log.debug("Setting Device Management Service Provider: '" +
                     deviceManagementService.getProviderType() + "'");
         }
+        synchronized (LOCK) {
             deviceManagers.add(deviceManagementService);
             for (PluginInitializationListener listener : listeners) {
                 listener.registerDeviceManagementService(deviceManagementService);
             }
         }
+    }
 
     /**
      * Unsets Device Management service.