Imp p_main_supplierinfo default sellers for variant

If no specific record are found by the first filter. The Odoo default
method will return all active supplier info.
Which will include also supplier info record related to other specific
variant.

With this change if some supplier info related to the product
variant exist, they will be returned instead.

product_main_supplierinfo/models/product_product.py

@@ -49,5 +49,7 @@ def _get_sellers(self):
             )
         )
         if not sellers:
-            sellers = all_sellers
+            sellers = all_sellers.filtered(lambda s: (s.product_id == self))
+            if not sellers:
+                sellers = all_sellers
         return sellers