When scrolling or zooming a graph we want to disable the page
refresh because we are trying to look at the detail. Unfortunately
Javascript cannot override the refresh meta tag;

<meta http-equiv="refresh" content="{$CONFIG['page_refresh']}">

Except with a window.stop() which is brutal but since the
complete RRD data has already been read this is not an issue.

See issue #139 suggesting submitting a PR to refresh RRD data
whilst a graph is scrolled or zoomed.