[ticket/12483] Close database connection when tearDown() is called

Similar to phpbb_database_test_case::tearDown()

PHPBB3-12483

tests/test_framework/phpbb_functional_test_case.php

@@ -108,6 +108,17 @@ class phpbb_functional_test_case extends phpbb_test_case
 		}
 	}
 
+	protected function tearDown()
+	{
+		parent::tearDown();
+
+		if ($this->db instanceof \phpbb\db\driver\driver_interface)
+		{
+			// Close the database connections again this test
+			$this->db->sql_close();
+		}
+	}
+
 	/**
 	* Perform a request to page
 	*