Properly destroy the timeout (for ajax/distribution) for a namespace mod...

When the users goes to `table/<id_table>`, we call `load_key_distr` which is going to make ajax requests to `/ajax/distribution?...` every 5 seconds.

We forgot somehow to call `clear_timeout` to remove the timeout/interval, meaning that if the users goes to a table and leaves and repeat both these two actions X times, we will make X requests to `/ajax/distribution...` every 5 seconds.