Do not process linkTypes that were already processed in plugins

Author: kassner

app/code/Magento/Catalog/Controller/Adminhtml/Product/Initialization/Helper.php

@@ -260,6 +260,11 @@ protected function setProductLinks(\Magento\Catalog\Model\Product $product)
             $linkTypes[$linkTypeObject->getName()] = $product->getData($linkTypeObject->getName() . '_readonly');
         }
 
+        // skip linkTypes that were already processed on initializeLinks plugins
+        foreach ($productLinks as $productLink) {
+            unset($linkTypes[$productLink->getLinkType()]);
+        }
+
         foreach ($linkTypes as $linkType => $readonly) {
             if (isset($links[$linkType]) && !$readonly) {
                 foreach ((array)$links[$linkType] as $linkData) {