service: fix bug, when criu reports success on dump fail

cr_dump_tasks() may return not only -1 on fail.
Signed-off-by: Ruslan Kuprieiev <kupruser@gmail.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

cr-service.c

@@ -175,7 +175,7 @@ static int dump_using_req(int sk, CriuOpts *req)
 		goto exit;
 	}
 
-	if (cr_dump_tasks(req->pid) == -1)
+	if (cr_dump_tasks(req->pid))
 		goto exit;
 
 	success = true;