[FIX] web: ViewManager: filter out some keys from context

A traceback occured when trying to create a BOM by going to
Inventory > Master Data > Products, on a product form view clicking
on the BOM stat button, and then on 'Create'.

This was a context problem: the context of the 'Products' action
was passed to the 'BOM' action without removing action specific
keys like 'default_*' or 'search_default_*'. For instance, it
contained a 'default_type' key, and as type is also a field of the
mrp.bom model, the python tried to interpret it, except that the
given value wasn't a correct value for mrp.bom.

When a button is clicked, we mix contexts coming from different
places to execute the new action. For some of them, we already
filtered out those action specific keys. This fix is simply to
make the piece of context adding the problematic keys pass though
the filter as well.