Ensure stable key order when processing hashes

Even though it might just be possible to create a stable
insertion order in other places, this should really
not be necessary. We want to generate stable icinga
config files without having to jump though any extra hoops.

lib/puppet_x/icinga2/utils.rb

@@ -241,7 +241,7 @@ def self.process_array(items, indent = 2)
 
     def self.process_hash(attrs, indent = 2, level = 3, prefix = ' ' * indent)
       result = ''
-      attrs.each do |attr, value_frozen|
+      attrs.sort.each do |attr, value_frozen|
         value = value_frozen.dup
         if value.is_a?(Puppet::Pops::Types::PSensitiveType::Sensitive)
           value = value.unwrap