Fix according review - change how we manage that plugin in a property array

Author: coderimus

app/code/Magento/Developer/Model/Di/PluginList.php

@@ -143,6 +143,10 @@ private function addPluginToList($pluginInstance, $pluginMethod, $methodTypes, $
     {
         if ($methodTypes & $typeCode) {
             if (!array_key_exists($pluginInstance, $this->pluginList[$this->pluginTypeMapping[$typeCode]])) {
+                $this->pluginList[$this->pluginTypeMapping[$typeCode]][$pluginInstance] = [];
+            }
+
+            if (!in_array($pluginMethod, $this->pluginList[$this->pluginTypeMapping[$typeCode]][$pluginInstance])) {
                 $this->pluginList[$this->pluginTypeMapping[$typeCode]][$pluginInstance][] = $pluginMethod;
             }
         }