[FIX] point_of_sale: exclude rescue sessions when getting current session

Rescue sessions have been added with revision
bed409322d

With this feature, this is possible to have multiple
pos sessions opened for a same user, if there are
rescue sessions.

`get_current_session` rely on the fact only one pos session
can be opened per user.

Rescue sessions are now excluded to get the current session, so:
 - at most one session can be found
 - rescue sessions cannot be resumed.

opw-652857

addons/point_of_sale/point_of_sale.py

@@ -42,7 +42,7 @@ class pos_config(osv.osv):
         result = dict()
 
         for record in self.browse(cr, uid, ids, context=context):
-            session_id = record.session_ids.filtered(lambda r: r.user_id.id == uid and not r.state == 'closed')
+            session_id = record.session_ids.filtered(lambda r: r.user_id.id == uid and not r.state == 'closed' and not r.rescue)
             result[record.id] = {
                 'current_session_id': session_id,
                 'current_session_state': session_id.state,