[FIX] web: reset dataset orderby on groupby filter.

If the list view had a default order,
for instance, default_order="create_date desc",
setting a groupby filter kept this default order
and the groupby list was therefore not ordered on the groupby field

In general, when setting a groupby filter on a list
we expect the list to be grouped by the groupby field

The reset of the orderby is done only when the list is not grouped
and a first groupby filter is applied.
The orderby is not reset when adding a new groupby,
when one was already applied.
It doesn't reset either when passing from 2 groupby clause to 1.
It doesn't reset either when passing from 1 groupby clause to none.

opw-627233

addons/web/static/src/js/views.js

@@ -860,6 +860,9 @@ instance.web.ViewManager =  instance.web.Widget.extend({
             if (_.isString(groupby)) {
                 groupby = [groupby];
             }
+            if (!controller.grouped && !_.isEmpty(groupby)){
+                self.dataset.set_sort([]);
+            }
             $.when(controller.do_search(results.domain, results.context, groupby || [])).then(function() {
                 self.view_completely_inited.resolve();
             });