`beforeUnload` should stop `keepaliveLoop` from running
`beforeUnload` should stop `keepaliveLoop` from running

Currently if we refresh the page right before the `keepaliveLoop` will trigger
(due to setTimeout), the tabs that were cleared by the `beforeUnload` method
will be restored by the `keepalive` method.

scaryzet/crosstab,tejacques/crosstab,tejacques/crosstab,tranphuoctien/crosstab,tejacques/crosstab,tranphuoctien/crosstab,scaryzet/crosstab