Replace node.set to node.default.

[sho-h]

To fix below error. on chef 14.5.33 + kibana_lwrp 3.0.2.
I replaced node.set to node.default simply.

================================================================================
Error executing action `create` on resource 'kibana_install[kibana]'
================================================================================

Chef::Node::AttributeDoesNotExistError
--------------------------------------
No attribute `node['set']' exists on
the current node. Specifically the `set' attribute is not
defined. Please make sure you have spelled everything correctly.

Cookbook Trace:
---------------
/etc/chef/local-mode-cache/cache/cookbooks/kibana_lwrp/libraries/install.rb:99:in `block (2 levels) in <class:KibanaInstall>'
/etc/chef/local-mode-cache/cache/cookbooks/kibana_lwrp/libraries/install.rb:51:in `block in <class:KibanaInstall>'

see: chef/chef@34a0920