(VDB-570) Handle duplicate storage diffs

- If processing a new diff for a row that already exists in the DB,
  ignore the error without logging or queueing
- If processing a queued diff for a row that already exists, remove
  it from the queue

cmd/execute.go

@@ -139,7 +139,7 @@ func execute() {
 func init() {
 	rootCmd.AddCommand(executeCmd)
 	executeCmd.Flags().BoolVarP(&recheckHeadersArg, "recheck-headers", "r", false, "whether to re-check headers for watched events")
-	executeCmd.Flags().DurationVarP(&queueRecheckInterval, "queue-recheck-interval", "q", 5 * time.Minute, "how often to recheck queued storage diffs")
+	executeCmd.Flags().DurationVarP(&queueRecheckInterval, "queue-recheck-interval", "q", 5*time.Minute, "how often to recheck queued storage diffs")
 }
 
 type Exporter interface {