[FIX] account: tax mapping logic was broken by 7508b7c

The original tax should not be applied
if at least one destination tax was
applied. It should only be applied if
explicitly included in target taxes.

(Re-)Fixes #2261

addons/account/partner.py

@@ -79,11 +79,13 @@ class account_fiscal_position(osv.osv):
     def map_tax(self, taxes):
         result = self.env['account.tax'].browse()
         for tax in taxes:
+            tax_count = 0
             for t in self.tax_ids:
                 if t.tax_src_id == tax:
                     if t.tax_dest_id:
+                        tax_count += 1
                         result |= t.tax_dest_id
-            else:
+            if not tax_count:
                 result |= tax
         return result