Fix config watch (#1670)

* add dirty overrite test case

* need version to figure out if config need update or not

* using nanosecond as version for two goroutine can run in same second

* config should check snapshot version when update

* set checksum of ChangeSet

Co-authored-by: Asim Aslam <asim@aslam.me>

config/default.go

@@ -82,6 +82,11 @@ func (c *config) run() {
 
 			c.Lock()
 
+			if c.snap.Version >= snap.Version {
+				c.Unlock()
+				continue
+			}
+
 			// save
 			c.snap = snap