Allow puppet-lint fail_on_warnings to be explicitly disabled

[nabertrand]

pdk-templates/moduleroot/Rakefile.erb

Lines 69 to 71 in d05508f

	<% if @configs['linter_fail_on_warnings'] -%>
	PuppetLint.configuration.fail_on_warnings = true
	<% end -%>

There doesn't seem to be a way to trivially disable puppet-lint fail_on_warnings in the lint rake task as the default is true via https://github.com/puppetlabs/puppetlabs_spec_helper/blob/01886e8fb8c9470e74ffde39445732ce06209125/lib/puppetlabs_spec_helper/rake_tasks.rb#L156 and the template only supports setting to true. Perhaps this fragment could be changed to something like this?

<% if @configs.include?('linter_fail_on_warnings') -%>
<% if @configs['linter_fail_on_warnings'] -%> 
PuppetLint.configuration.fail_on_warnings = true 
<% else -%>
PuppetLint.configuration.fail_on_warnings = false
<% end -%>
<% end -%> 

This would also match the description of the setting:

linter_fail_on_warnings	A boolean indicating if the linter should exit non-zero on warnings as well as failures. Does affect .puppet-lint.rc.