This rev. strengthens the handling of concurrent actions of type
'ir.actions.act_window' in the ActionManager. In particular, the
two following cases are now handled:
- execute an action A, its 'load_views' RPC takes a while, during
that time, execute an action B: A can be dropped, meaning that
it doesn't need to fetch its data, and thus it should not be
appended to the DOM (nor appear in the breadcrumbs) ;
- execute an action A, its 'read' or 'search_read' RPC takes a
while, during that time, execute an action B: A can be dropped
and should not be appended to the DOM (nor appear in the
breadcrumbs).