Skip some tests using raw MySQL queries

Author: swissspidy

features/site-empty.feature

@@ -1,5 +1,6 @@
 Feature: Empty a WordPress site of its data
 
+  @require-mysql
   Scenario: Empty a site
     Given a WP installation
     And I run `wp option update uploads_use_yearmonth_folders 0`

features/site-option.feature

@@ -127,6 +127,7 @@ Feature: Manage WordPress site options
       """
     And the return code should be 1
 
+  @require-mysql
   Scenario: Filter options by `--site_id`
     Given a WP multisite installation