[FIX] strip group name before calling has_group

user_has_groups is used to check for groups in e.g. view attributes (`@groups`).
When trying to format lists of groups in views, it would break down as it would 
pass e.g. `\n        some.group` to `res.users.has_group`, which would look for 
an xid with the module `\n        some` and (oddly enough) not find it.

Theoretically could also handle that inside res.users.has_group but it seems
ever-so-slightly more risky, and has_group is only used programmatically and 
should thus already be called correctly.

fixes #9797

openerp/models.py

@@ -1372,7 +1372,7 @@ class BaseModel(object):
            :return: True if the current user is a member of one of the
                     given groups
         """
-        return any(self.pool['res.users'].has_group(cr, uid, group_ext_id)
+        return any(self.pool['res.users'].has_group(cr, uid, group_ext_id.strip())
                    for group_ext_id in groups.split(','))
 
     def _get_default_form_view(self, cr, user, context=None):