(GH-189) Fix module root for validation

Previously in commit c70511b validation was changed to initialise Puppet Lint
correctly, however there was a typo in the provider.  This commit fixes the
typo and references the correct variable.

Author: glennsarti

lib/puppet-languageserver/manifest/validation_provider.rb

@@ -116,7 +116,7 @@ def self.init_puppet_lint(root_dir, lint_options = [])
           linter_options = PuppetLint::OptParser.build
         else
           begin
-            Dir.chdir(module_root.to_s) { linter_options = PuppetLint::OptParser.build }
+            Dir.chdir(root_dir.to_s) { linter_options = PuppetLint::OptParser.build }
           rescue OptionParser::InvalidOption => e
             PuppetLanguageServer.log_message(:error, "(#{name}) Error reading Puppet Lint configuration.  Using default: #{e}")
             linter_options = PuppetLint::OptParser.build