[ONOS-7570] ServiceNotFoundException(DriverService) in de-serializing DefaultGroup

Change-Id: I0365f92379d87ca22ef23fb0b721da4a42def664
diff --git a/core/store/dist/src/main/java/org/onosproject/store/group/impl/DistributedGroupStore.java b/core/store/dist/src/main/java/org/onosproject/store/group/impl/DistributedGroupStore.java
index 1335087..d8c3f7c 100644
--- a/core/store/dist/src/main/java/org/onosproject/store/group/impl/DistributedGroupStore.java
+++ b/core/store/dist/src/main/java/org/onosproject/store/group/impl/DistributedGroupStore.java
@@ -35,6 +35,7 @@
 import org.onosproject.mastership.MastershipService;
 import org.onosproject.net.DeviceId;
 import org.onosproject.net.MastershipRole;
+import org.onosproject.net.driver.DriverService;
 import org.onosproject.net.group.DefaultGroup;
 import org.onosproject.net.group.DefaultGroupBucket;
 import org.onosproject.net.group.DefaultGroupDescription;
@@ -130,6 +131,11 @@
     @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
     protected ComponentConfigService cfgService;
 
+    // Guarantees enabling DriverService before enabling GroupStore
+    // (DriverService is used in serializing/de-serializing DefaultGroup)
+    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
+    protected DriverService driverService;
+
     private ScheduledExecutorService executor;
     private Consumer<Status> statusChangeListener;
     // Per device group table with (device id + app cookie) as key