[FIX] website_sale: attribute conflict with m2m tags color

The color field of a product.attribute.value enable users to choose a
color with its HTML color value (hexa, named, rgb, rgba).

In the many2many tags the color field on the model has a magic feature
which color the tag in several instances. But these color are numbered
from 0 to 10 and are incompatible with HTML color values.

So with with the model product.attribute.value, the many2many tags
widget would use the color system (since a field name color exists), and
when setting a color with it, it would be invalid and erase the wanted
named or HTML value color.

This fix ignore the setting of the tag color for this particular model,
a following fix (in master) should rename the column to properly fix
this.

opw-653124

addons/website_sale/models/product.py

@@ -190,3 +190,10 @@ class product_attribute_value(osv.Model):
     _columns = {
         'color': fields.char("HTML Color Index", help="Here you can set a specific HTML color index (e.g. #ff0000) to display the color on the website if the attibute type is 'Color'."),
     }
+
+    # TODO in master: remove this function and change 'color' field name
+    def write(self, cr, uid, ids, vals, context=None):
+        # ignore write coming from many2many_tags color system
+        if vals.keys() == ['color'] and isinstance(vals['color'], (int, long)):
+            vals = {}
+        return super(product_attribute_value, self).write(cr, uid, ids, vals, context=context)