[FIX] web: search view: autocomplete on datetime fields

... gives wrong values due to the timezone.

For instance, let's assume that the browser timezone of the user
is UTC+2, and the user types 10/09/2017 10:00:00 in a searchview
with a datetime field in its arch (i.e. which autocompletes on a
datatime field). Before this rev., the suggested value was
10/09/2017 08:00:00, i.e. the timezone offset was substracted from
the value.

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

@@ -351,7 +351,8 @@ var DateField = Field.extend(/** @lends instance.web.search.DateField# */{
             return $.when(null);
         }
 
-        var m = moment(v, t === 'datetime' ? 'YYYY-MM-DD HH:mm:ss' : 'YYYY-MM-DD');
+        // THIS SHOULD BE FORWARDPORTED UP TO SAAS-15, NOT LATER
+        var m = moment.utc(v, t === 'datetime' ? 'YYYY-MM-DD HH:mm:ss' : 'YYYY-MM-DD');
         if (!m.isValid()) { return $.when(null); }
         var d = m.toDate();
         var date_string = formats.format_value(d, this.attrs);