[FIX] tools: avoid duplicates when synchronising translation

The "Synchronise translation" wizard almost doubles the number of translated
terms in database.
This is due to the loss of the module reference at the synchronisation
(`module_name` is empty as updating all modules)
Only overwrite the module when it is set (default None)
Fixes #6149

Second part of the patches avoid inserting translations without any module for
locale xml ids.

openerp/tools/translate.py

@@ -1031,7 +1031,8 @@ def trans_load_data(cr, fileobj, fileformat, lang, lang_name=None, verbose=True,
             if isinstance(res_id, (int, long)) or \
                     (isinstance(res_id, basestring) and res_id.isdigit()):
                 dic['res_id'] = int(res_id)
-                dic['module'] = module_name
+                if module_name:
+                    dic['module'] = dic['module']
             else:
                 # res_id is an xml id
                 dic['res_id'] = None
@@ -1039,7 +1040,7 @@ def trans_load_data(cr, fileobj, fileformat, lang, lang_name=None, verbose=True,
                 if '.' in res_id:
                     dic['module'], dic['imd_name'] = res_id.split('.', 1)
                 else:
-                    dic['module'], dic['imd_name'] = False, res_id
+                    dic['module'], dic['imd_name'] = module_name, res_id
 
             irt_cursor.push(dic)