Issue #1882584 by Berdir: Improve concurrent testing by avoiding unecessary persistent rebuilds.

core/modules/simpletest/lib/Drupal/simpletest/WebTestBase.php

@@ -900,18 +900,6 @@ protected function tearDown() {
     $this->loggedInUser = FALSE;
     $this->additionalCurlOptions = array();
 
-    // Reload module list and implementations to ensure that test module hooks
-    // aren't called after tests.
-    system_list_reset();
-    module_list_reset();
-    module_implements_reset();
-
-    // Reset the Field API.
-    field_cache_clear();
-
-    // Rebuild caches.
-    $this->refreshVariables();
-
     // Close the CURL handler.
     $this->curlClose();
   }