MC-6273: Mysql url_rewrite select make on product view page 170+ times per request

- fixed unit tests

Author: vgoncharenko

lib/internal/Magento/Framework/Cache/LockGuardedCacheLoader.php

@@ -58,7 +58,7 @@ public function __construct(
      * @param callable $dataLoader
      * @param callable $dataCollector
      * @param callable $dataSaver
-     * @return array
+     * @return mixed
      */
     public function lockedLoadData(
         string $lockName,

lib/internal/Magento/Framework/View/Element/AbstractBlock.php

@@ -1084,7 +1084,7 @@ protected function getCacheLifetime()
     /**
      * Load block html from cache storage
      *
-     * @return string|false
+     * @return string
      */
     protected function _loadCache()
     {
@@ -1126,7 +1126,7 @@ protected function _loadCache()
             }
         };
 
-        return $this->lockQuery->lockedLoadData(
+        return (string)$this->lockQuery->lockedLoadData(
             $this->getCacheKey(),
             $loadAction,
             $collectAction,