[FIX] groupby groups fetching of their ancestor searchview

[FIX] groupby groups fetching of their ancestor searchview

Implementation of invisibles in search view altered handling of search
inputs: their parent may not be the searchview anymore (usually is a
instance.web.search.Group). GroupbyGroup assumed parent was view and
was actually unused until
xmo@openerp.com-20130307124222-1ypzfopbktxmad4z, which exposed the
incorrect underlying assumption.

Make GroupbyGroup access its view when it wants its view, not its
parent.

bzr revid: xmo@openerp.com-20130312092824-z7sh4h3ityo4g00v