Fix $manage_index if statement

Without this patch, with puppet 3, if the $manage_index variable is set,
it is ignored, since the conditional compares the string 'manage_index'
to the value 'true'. With puppet 4, this would cause a syntax error.

Change-Id: If9dc13515059a2c148ddde3108b256feb3bc1298

manifests/site.pp

@@ -31,7 +31,7 @@ define meetbot::site(
     ensure => directory,
   }
 
-  if manage_index == true {
+  if $manage_index == true {
     file { "${meetbot}/index.html":
       ensure  => present,
       content => template('meetbot/index.html.erb'),