MAGETWO-58594: Static Assets deployment throws errors when redis is used for cache after PR 389

added description for dummy cache adapter

Author: AVoskoboinikov

lib/internal/Magento/Framework/App/Cache/Type/Dummy.php

@@ -7,6 +7,12 @@
 
 use Magento\Framework\App\CacheInterface;
 
+/**
+ * Dummy cache adapter
+ *
+ * for cases when need to disable interaction with cache
+ * but no specific cache type is used
+ */
 class Dummy implements CacheInterface
 {
     /**