[ONOS-6721] Add dependency of FlowRuleManager on DriverService to ensure driver service is bound prior to usage.

Change-Id: I1f0b60e8fdbcb1d6fcf7bbd4028478140e12669d
diff --git a/core/net/src/main/java/org/onosproject/net/flow/impl/FlowRuleManager.java b/core/net/src/main/java/org/onosproject/net/flow/impl/FlowRuleManager.java
index 6c47560..81cf1c8 100644
--- a/core/net/src/main/java/org/onosproject/net/flow/impl/FlowRuleManager.java
+++ b/core/net/src/main/java/org/onosproject/net/flow/impl/FlowRuleManager.java
@@ -40,6 +40,7 @@
 import org.onosproject.net.device.DeviceEvent;
 import org.onosproject.net.device.DeviceListener;
 import org.onosproject.net.device.DeviceService;
+import org.onosproject.net.driver.DriverService;
 import org.onosproject.net.flow.CompletedBatchOperation;
 import org.onosproject.net.flow.DefaultFlowEntry;
 import org.onosproject.net.flow.FlowEntry;
@@ -148,6 +149,9 @@
     @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
     protected ComponentConfigService cfgService;
 
+    @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
+    protected DriverService driverService;
+
     @Activate
     public void activate(ComponentContext context) {
         modified(context);