MAGETWO-97311: 2.3 only - creating attribute option value using API returns unexpected response

- Clear attribte options after saving attribute.

Author: AlexeyManenok

app/code/Magento/Catalog/Model/ResourceModel/Eav/Attribute.php

@@ -236,6 +236,9 @@ public function afterSave()
         ) {
             $this->_indexerEavProcessor->markIndexerAsInvalid();
         }
+        if ($this->_source !== null) {
+            $this->_source->clearOptions();
+        }
 
         return parent::afterSave();
     }

app/code/Magento/Eav/Model/Entity/Attribute/Source/AbstractSource.php

@@ -80,6 +80,8 @@ public function getOptionText($value)
     }
 
     /**
+     * Get option id.
+     *
      * @param string $value
      * @return null|string
      */
@@ -93,6 +95,16 @@ public function getOptionId($value)
         return null;
     }
 
+    /**
+     * Clear cached options.
+     *
+     * @return void
+     */
+    public function clearOptions() : void
+    {
+        $this->_options = null;
+    }
+
     /**
      * Add Value Sort To Collection Select
      *