Removed ClockService<K, V> and replaced its usage with a BiFunction<K, V, Timestamp>

Change-Id: Ide8d979f9361f1aff6727a83733747f4512ef8ff
diff --git a/core/store/dist/src/main/java/org/onosproject/store/device/impl/GossipDeviceStore.java b/core/store/dist/src/main/java/org/onosproject/store/device/impl/GossipDeviceStore.java
index de6b523..842274a 100644
--- a/core/store/dist/src/main/java/org/onosproject/store/device/impl/GossipDeviceStore.java
+++ b/core/store/dist/src/main/java/org/onosproject/store/device/impl/GossipDeviceStore.java
@@ -78,7 +78,6 @@
 import org.onosproject.store.service.MultiValuedTimestamp;
 import org.onosproject.store.service.StorageService;
 import org.onosproject.store.service.WallClockTimestamp;
-import org.onosproject.store.service.WallclockClockManager;
 import org.slf4j.Logger;
 
 import java.io.IOException;
@@ -244,7 +243,7 @@
                 .withName("port-stats")
                 .withSerializer(deviceDataSerializer)
                 .withAntiEntropyPeriod(5, TimeUnit.SECONDS)
-                .withClockService(new WallclockClockManager<>())
+                .withTimestampProvider((k, v) -> new WallClockTimestamp())
                 .withTombstonesDisabled()
                 .build();
         devicePortStats.addListener(portStatsListener);