UI Spring Context Holder bean registration (#1026)

* register the Spring Context Holder bean for UI instead of setting the context for each UI separately
* reverted test scope for db driver

Signed-off-by: Bogdan Bondar <Bogdan.Bondar@bosch.io>

hawkbit-repository/hawkbit-repository-core/src/main/java/org/eclipse/hawkbit/repository/model/helper/EventPublisherHolder.java

@@ -35,7 +35,7 @@ public final class EventPublisherHolder {
     }
 
     /**
-     * @return the cache manager holder singleton instance
+     * @return the event publisher holder singleton instance
      */
     public static EventPublisherHolder getInstance() {
         return SINGLETON;