Fix NoMethodError undefined method call for Hash

Enumerable#find expects a callable object for its `ifnone` parameter.

lib/cap-ec2/utils.rb

@@ -23,7 +23,7 @@ def stages_tag
     end
 
     def tag_value(instance, key)
-      instance.tags.find({}) { |t| t[:key] == key.to_s }[:value]
+      instance.tags.find(-> { {} }) { |t| t[:key] == key.to_s }[:value]
     end
 
     def self.contact_point_mapping