Merge pull request #271 from criteo-forks/explicit_sparse_mode

Make sure sparse mode is used on secrets where it is explicit

lib/chef-vault/item_keys.rb

@@ -39,7 +39,7 @@ def [](key)
       ckey = @cache[key]
       return ckey unless ckey.nil?
       # check if the key is saved in sparse mode
-      skey = sparse_key(sparse_id(key))
+      skey = sparse_key(sparse_id(key)) if sparse?
       if skey
         skey[key]
       else
@@ -213,6 +213,10 @@ def self.load(vault, name)
 
     # @private
 
+    def sparse?
+      @raw_data["mode"] == "sparse"
+    end
+
     def sparse_id(key, item_id = @raw_data["id"])
       "#{item_id.chomp("_keys")}_key_#{key}"
     end