Fix applying createdat less or equal to rollout group filter (#1765)

Signed-off-by: Marinov Avgustin <Avgustin.Marinov@bosch.com>

hawkbit-repository/hawkbit-repository-core/src/main/java/org/eclipse/hawkbit/repository/RolloutHelper.java

@@ -110,7 +110,7 @@ public final class RolloutHelper {
      */
     public static String getTargetFilterQuery(final String targetFilter, final Long createdAt) {
         if (createdAt != null) {
-            return targetFilter + ";createdat=le=" + createdAt.toString();
+            return "(" + targetFilter + ");createdat=le=" + createdAt;
         }
         return targetFilter;
     }