feat: disable disksup by default

apps/emqx/etc/vm.args.cloud

@@ -113,3 +113,6 @@
 ## Mnesia thresholds
 -mnesia dump_log_write_threshold 5000
 -mnesia dump_log_time_threshold 60000
+
+## Disable os_mon's disksup by default
+-os_mon start_disksup false