Add better puppet-agent detection

Previously the default behaviour was to use ruby in the path however some puppet
agent installations do not put its ruby on the path and is instead located in
/opt/puppetlabs/puppet/bin/ruby. This commit adds file detection to prefer the
specific puppet agent location of ruby and fall back to just the path.

Author: glennsarti

client/src/connection.ts

@@ -209,7 +209,13 @@ export class ConnectionManager implements IConnectionManager {
         break;
       default:
         myOutputChannel.appendLine('Starting language server')
-        cmd = 'ruby'
+
+        // Try and find the puppet-agent ruby
+        let rubyPath: string = '/opt/puppetlabs/puppet/bin/ruby';
+        if (fs.existsSync(rubyPath)) { cmd = rubyPath }
+
+        // Default to ruby on the path
+        if (cmd == undefined) { cmd = 'ruby' }
         options = {
           shell: true,
           env: process.env,