Prevent duplicated CAF entries with product attributes

The script now correctly adds all occurences of each name.
However, when product attribute is used, it'll be checked twice.
Prevent the second check by storing all found names in arrays and only
append to caf_additions when it's not in there.
diff --git a/cm_crowdin_sync.py b/cm_crowdin_sync.py
index 26eddcc..289660b 100755
--- a/cm_crowdin_sync.py
+++ b/cm_crowdin_sync.py
@@ -76,22 +76,31 @@
     # Store all differences in this list
     caf_additions = []
 
+    # Store all found strings/arrays/plurals.
+    # Prevent duplicates with product attribute
+    found_string = []
+    found_string_array = []
+    found_plurals = []
+
     # Add all CAF additions to the list 'caf_additions'
     for z in names_cm_string:
-        if z not in names_base_string:
+        if z not in names_base_string and z not in found_string:
             for string_item in list_cm_string:
                 if string_item.attributes['name'].value == z:
                     caf_additions.append('    ' + string_item.toxml())
+            found_string.append(z)
     for y in names_cm_string_array:
-        if y not in names_base_string_array:
+        if y not in names_base_string_array and y not in found_string_array:
             for string_array_item in list_cm_string_array:
                 if string_array_item.attributes['name'].value == y:
                     caf_additions.append('    ' + string_array_item.toxml())
+            found_string_array.append(y)
     for x in names_cm_plurals:
-        if x not in names_base_plurals:
+        if x not in names_base_plurals and x not in found_plurals:
             for plurals_item in list_cm_plurals:
                 if plurals_item.attributes['name'].value == x:
                     caf_additions.append('    ' + plurals_item.toxml())
+            found_plurals.append(x)
 
     # Done :-)
     return caf_additions