[Seaside] Seaside Page expired problem, probably related to liveCallback links

[Philippe Marschall]

> Seems it is related
> to number of images in the folder, and therefore number of links on the page.

This sounds familiar. Live actions use continuations and the maximum
size of the continuation chache is only 20.

A quick and dirty hack is do change the #initialize of WALRUCache and
set max to a bigger value like 40.